Systems and methods for desalinating aqueous compositions through hetero-azeotropic distillation

ABSTRACT

A method of desalinating an aqueous composition includes forming a hetero-azeotrope mixture by combining the aqueous composition with an entrainer, the aqueous composition including at least one salt, and subjecting the hetero-azeotrope mixture to distillation at a distillation temperature of less than the boiling temperature of the aqueous composition for an operating distillation pressure, resulting in separating the hetero-azeotrope mixture into a distillation bottoms liquid and a multi-phase condensate. The method includes recovering the multi-phase condensate having an entrainer-rich phase and an aqueous phase, the aqueous phase comprising desalinated water, and removing a portion of the aqueous phase from the multi-phase condensate to recover the desalinated water. Systems for conducting the method of desalinating an aqueous stream are also disclosed.

TECHNICAL FIELD

The present specification generally relates to systems and methods fordesalinating aqueous compositions, in particular, systems and methodsthat include hetero-azeotropic distillation for desalinating aqueouscompositions.

BACKGROUND

Petroleum drilling, production, and refining operations can producevarious aqueous streams, such as produced water for example, that havevaried salt concentrations and include dissolved and undissolved organiccompounds, such as oil residues or droplets, phenolic compounds, polymercompounds from drilling fluids and production chemicals, and otherorganic and inorganic contaminants. The salinity of produced water andother aqueous streams from oil drilling, production, or refining rendersthese aqueous streams unsuitable for many applications, such as use indrilling, oil desalting, anthropologic or agricultural uses, or otherapplications.

Processes such as membrane distillation, reverse osmosis, other membraneprocesses, thin film evaporation, vacuum distillation, multi-stage flashdistillation (MSF), multiple-effect distillation (MED), mechanical orthermal vapor-compression evaporation, electro-dialysis, ion exchange,and other separation processes have been developed for removing saltsfrom aqueous streams. For membrane-based separation processes, such asmembrane distillation, reverse osmosis, or other membrane processes, thepresence of oil droplets and other organic and inorganic constituents inaqueous streams from petroleum drilling, production, and refiningoperations renders these existing methods ineffective for desalinatingthe aqueous streams from petroleum operations. For example, oil dropletsand other organic constituents of produced water may cause fouling ofmembranes employed in various membrane processes. Thermal separationmethods, such as the various distillation methods previously discussed,require substantial energy demands as well as large equipment sizes(footprint and height) to desalinate large volumes of water.Additionally, some of these existing methods are not suitable from asafety standpoint in oxygen-free environments, such as petroleumdrilling, production, or refining operations. In these oxygen-freeenvironments, treatment processes must not require contact with orproduction of oxygen or compounds capable of providing a source of freeoxygen, such as compounds commonly used in chemical treatments to removeorganic compounds. Because of these constraints, produced water andother aqueous streams from petroleum drilling, production, or refiningoperations cannot be desalinating safely and effectively using currentlyavailable desalination technologies.

SUMMARY

Accordingly, ongoing needs exist for improved methods of desalinatingaqueous compositions, such as produced water and other aqueous streamsthat include various salts as well as organic constituents or oilyresidues. The processes and systems of the present disclosure include ahetero-azeotropic distillation process in which the aqueous composition,such as produced water for example, is combined with one or moreentrainers to form a hetero-azeotrope having a hetero-azeotropic boilingtemperature that is less than the boiling temperature of the aqueouscomposition by itself. The entrainers include organic compounds that areimmiscible with water or have reduced-miscibility with water, arenon-reactive with water and other constituents of the aqueouscomposition, and do not result in introducing free-oxygen to the aqueouscomposition. The hetero-azeotropic distillation process may be conductedat a reduced distillation temperature, which enables a compact andeconomical water desalination process based on short-path distillationdriven by industrial, or environmental, waste heat. Desalination of theaqueous composition through short-path hetero-azeotropic distillationmay reduce the energy load of the desalination process to produce adesalinated water stream that does not have free oxygen. The processesand systems of the present disclosure can include additional unitoperations, such as crystallizers and other water treatment processes,to further treat portions of the aqueous composition.

According to some aspects of the present disclosure, a method fordesalinating an aqueous composition includes forming a hetero-azeotropemixture by combining at least a portion of the aqueous composition withat least one entrainer, the at least a portion of the aqueouscomposition comprising at least one salt. The method includes subjectingthe hetero-azeotrope mixture to distillation at a distillationtemperature of less than a boiling temperature of the aqueouscomposition at an operating distillation pressure, which results inseparation of the hetero-azeotrope mixture into a distillation bottomsliquid and a multi-phase condensate. The method further includesrecovering the multi-phase condensate. The multi-phase condensateincludes at least an entrainer-rich phase and an aqueous phase, theaqueous phase comprising desalinated water. The method includes removingat least a portion of the aqueous phase from the multi-phase condensateto recover the desalinated water. The method may further includesubjecting at least a portion of the distillation bottoms liquid tocrystallization which results in separation of the distillation bottomsliquid into a salt product and a brine composition.

According to one or more other aspects of the present disclosure, asystem for desalinating an aqueous composition includes a distillationsystem comprising a distillation vessel in thermal communication with aheat source and a condenser in fluid communication with the distillationvessel. The system includes a condensate receiver in fluid communicationwith the condenser and operable to receive a multi-phase condensatecomprising at least an aqueous phase and an entrainer-rich phase fromthe distillation system. The condensate receiver may include aseparation system operable to separate at least a portion of an aqueousphase from the condensate. The system may further include a crystallizerin fluid communication with the distillation vessel, the crystallizeroperable to receive a bottoms liquid from the distillation vessel andseparate at least a portion of a salt in the bottoms liquid to produce asalt product and a brine composition.

Additional features and advantages of the present disclosure will be setforth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the described subject matter, including thedetailed description which follows, the claims, as well as the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific aspects of the presentdisclosure can be best understood when read in conjunction with thefollowing drawings, in which like structure is indicated with likereference numerals and in which:

FIG. 1 schematically depicts a process flow diagram for a system fordesalinating an aqueous composition, according to one or moreembodiments described in this disclosure;

FIG. 2 graphically depicts a phase equilibrium diagram for an azeotropeof water and 1-butanol;

FIG. 3 graphically depicts a mass fraction of water in a vapor phase(y-axis) and hetero-azeotrope boiling temperature (x-axis) for aplurality of hetero-azeotropes formed with water and various entrainercompounds, according to one or more embodiments described in thisdisclosure;

FIG. 4A graphically depicts a phase equilibrium diagram for a ternaryhetero-azeotrope of water, benzene, and toluene at a pressure of 1 bar(100 kPa), according to one or more embodiments described in thisdisclosure;

FIG. 4B graphically depicts a phase equilibrium diagram for a ternaryhetero-azeotrope of water, benzene, and toluene at a pressure of 3.5 bar(350 kPa), according to one or more embodiments described in thisdisclosure;

FIG. 5 graphically depicts a phase equilibrium diagram for a ternaryhetero-azeotrope of water, benzene, and n-pentane at a pressure of 3.5bar (350 kPa), according to one or more embodiments described in thisdisclosure;

FIG. 6 graphically depicts a phase equilibrium diagram for a ternaryhetero-azeotrope of water, toluene, and n-pentane at a pressure of 3.5bar (350 kPa), according to one or more embodiments described in thisdisclosure;

FIG. 7 schematically depicts a distillation system of the system of FIG.1, according to one or more embodiments described in this disclosure;

FIG. 8A schematically depicts an embodiment of a configuration of acondenser and a condensate receiver relative to a distillation column ofthe system of FIG. 1, according to one or more embodiments described inthis disclosure;

FIG. 8B schematically depicts another embodiment of a configuration of acondenser and a condensate receiver relative to a distillation column ofthe system of FIG. 1, according to one or more embodiments described inthis disclosure;

FIG. 8C schematically depicts yet another embodiment of a configurationof a condenser and a condensate receiver relative to a distillationcolumn of the system of FIG. 1, according to one or more embodimentsdescribed in this disclosure;

FIG. 8D schematically depicts still another embodiment of aconfiguration of a condenser and a condensate receiver relative to adistillation column of the system of FIG. 1, according to one or moreembodiments described in this disclosure;

FIG. 9 schematically depicts another embodiment of a system forconducting a process for desalinating an aqueous composition includingheat management and recovery from a distillation process of the system,according to one or more embodiments described in this disclosure;

FIG. 10 schematically depicts another embodiment of a system fordesalinating an aqueous stream that includes a distillation feedstreamcrystallization process, according to one or more embodiments describedin this disclosure;

FIG. 11 schematically depicts an embodiment of the system of FIG. 10including heat management and recovery from a distillation process ofthe system, according to one or more embodiments described in thisdisclosure;

FIG. 12 schematically depicts an experimental apparatus for conductingthe experiments in Examples 1 through 5, according to one or moreembodiments described in this disclosure;

FIG. 13 graphically depicts a bulk temperature of a hetero-azeotropemixture (y-axis) as a function of time (x-axis) for a plurality ofhetero-azeotrope mixtures that include a fixed amount of tolueneentrainer with varying amounts of an aqueous composition, according toone or more embodiments described in this disclosure;

FIG. 14 graphically depicts a volume of desalinated water collected(y-axis) as a function of time (x-axis) for the plurality ofhetero-azeotrope mixtures of FIG. 13, according to one or moreembodiments described in this disclosure;

FIG. 15 graphically depicts a temperature of the vapor phase (y-axis) asa function of time (x-axis) for the hetero-azeotrope mixtures of FIG.13, according to one or more embodiments described in this disclosure;

FIG. 16 graphically depicts the bulk temperature of the hetero-azeotropemixtures of FIG. 13 (y-axis) as a function of time (x-axis) for the timeperiod after the start of vaporization of the hetero-azeotrope mixtures,according to one or more embodiments described in this disclosure;

FIG. 17 graphically depicts a bulk temperature of a hetero-azeotropemixture (y-axis) as a function of time (x-axis) for a plurality ofhetero-azeotrope mixtures including a fixed amount of aqueouscomposition with varying amounts of toluene entrainer, according to oneor more embodiments described in this disclosure;

FIG. 18 graphically depicts a volume of desalinated water collected(y-axis) as a function of time (x-axis) for the plurality ofhetero-azeotrope mixtures of FIG. 17, according to one or moreembodiments described in this disclosure;

FIG. 19 graphically depicts a temperature of the vapor phase (y-axis) asa function of time (x-axis) for the hetero-azeotrope mixtures of FIG.17, according to one or more embodiments described in this disclosure;

FIG. 20 graphically depicts the bulk temperature of the hetero-azeotropemixtures of FIG. 17 (y-axis) as a function of time (x-axis) for the timeperiod after the start of vaporization of the hetero-azeotrope mixtures,according to one or more embodiments described in this disclosure;

FIG. 21 graphically depicts a volume of desalinated water collected(y-axis) as a function of time (x-axis) for a plurality ofhetero-azeotrope mixtures that include toluene entrainer combined withaqueous compositions of varying salinity, according to one or moreembodiments described in this disclosure;

FIG. 22 graphically depicts a distillation rate (y-axis) as a functionof salinity of the aqueous composition (x-axis) for the hetero-azeotropemixtures of FIG. 21, according to one or more embodiments described inthis disclosure;

FIG. 23 graphically depicts a temperature of the vapor phase (y-axis) asa function of time (x-axis) for the hetero-azeotrope mixtures of FIG.21, according to one or more embodiments described in this disclosure;

FIG. 24 graphically depicts the bulk temperature of the hetero-azeotropemixtures of FIG. 21 (y-axis) as a function of time (x-axis) for the timeperiod after the start of vaporization of the hetero-azeotrope mixtures,according to one or more embodiments described in this disclosure;

FIG. 25 graphically depicts a bulk temperature of a ternaryhetero-azeotrope mixture (y-axis) as a function of time (x-axis) for aplurality of ternary hetero-azeotrope mixtures including an aqueouscomposition and toluene and n-pentane as entrainers, according to one ormore embodiments described in this disclosure;

FIG. 26 graphically depicts the bulk temperature of the hetero-azeotropemixtures of FIG. 25 (y-axis) as a function of time (x-axis) for timeafter the start of vaporization of the hetero-azeotrope mixtures,according to one or more embodiments described in this disclosure;

FIG. 27 graphically depicts a volume of desalinated water collected(y-axis) as a function of time (x-axis) for the plurality ofhetero-azeotrope mixtures of FIG. 25, according to one or moreembodiments described in this disclosure;

FIG. 28 graphically depicts a temperature of the vapor phase (y-axis) asa function of time (x-axis) for the hetero-azeotrope mixtures of FIG.25, according to one or more embodiments described in this disclosure;and

FIG. 29 graphically depicts a phase equilibrium diagram for a ternaryhetero-azeotrope of water, toluene, and n-pentane at ambient pressure,according to one or more embodiments described in this disclosure.

For the purpose of describing the simplified schematic illustrations anddescriptions of FIGS. 1, 7, 8A, 8B, 8C, 8D, 9, 10, and 11, the numerousvalves, temperature sensors, electronic controllers, and the like thatmay be employed and well known to those of ordinary skill in the art ofcertain chemical processing operations are not included. Further,accompanying components that are often included in typical chemicalprocessing operations, such as valves, pipes, pumps, heat exchangers,instrumentation, internal vessel structures, or other subsystems may notbe depicted. Though not depicted, it should be understood that thesecomponents are within the spirit and scope of the present disclosure.However, operational components, such as those described in the presentdisclosure, may be added to the systems and processes described in thisdisclosure.

Arrows in the drawings refer to process streams. However, the arrows mayequivalently refer to transfer lines which may serve to transfer processstreams between two or more system components. Additionally, arrows thatconnect to system components may define inlets or outlets in each givensystem component. The arrow direction corresponds generally with themajor direction of movement of the materials of the stream containedwithin the physical transfer line signified by the arrow. Furthermore,arrows which do not connect two or more system components may signify aproduct stream which exits the depicted system or a system inlet streamwhich enters the depicted system. Product streams may be furtherprocessed in accompanying chemical processing systems or may becommercialized as end products.

Additionally, arrows in the drawings may schematically depict processsteps of transporting a stream from one system component to anothersystem component. For example, an arrow from one system componentpointing to another system component may represent “passing” a systemcomponent effluent to another system component, which may include thecontents of a process stream “exiting” or being “removed” from onesystem component and “introducing” the contents of that product streamto another system component.

It should be understood that two or more process streams are “mixed” or“combined” when two or more lines intersect in the schematic flowdiagrams of FIGS. 1, 7, 8A, 8B, 8C, 8D, 9, 10, and 11. Mixing orcombining may also include mixing by directly introducing both streamsinto a like system component, such as a distillation vessel,crystallizer, or other system component. For example, it should beunderstood that when two streams are depicted as being combined directlyprior to entering a system component, the streams could equivalently beintroduced into the system component separately and be mixed in thesystem component.

Reference will now be made in greater detail to various aspects of thepresent disclosure, some aspects of which are illustrated in theaccompanying drawings. Whenever possible, the same reference numeralswill be used throughout the drawings to refer to the same or similarparts.

DETAILED DESCRIPTION

The present disclosure is directed to methods, processes, and systemsfor desalinating aqueous compositions that include at least one salt andmay include one or more than one organic constituent. The methods andprocesses for desalinating the aqueous composition of the presentdisclosure include forming a hetero-azeotrope mixture by combining theaqueous composition with at least one entrainer. The aqueous compositionincludes at least one salt. Addition of the entrainer to the aqueouscomposition forms a hetero-azeotrope having a hetero-azeotrope boilingtemperature less than the boiling temperature of the aqueouscomposition. The methods and processes further include subjecting thehetero-azeotrope mixture to distillation at a distillation temperatureof less than the boiling temperature of the aqueous composition at anoperating distillation pressure (such as less than 100° C. at 1atmosphere (101.325 kilopascals) for pure water for example), which mayresult in separation of the hetero-azeotrope mixture into a two-phasecondensate and a distillation bottoms liquid, and recovering thetwo-phase condensate from the distillation. The two-phase condensate mayinclude a plurality of liquid phases such as an entrainer-rich phase andan aqueous phase, which includes desalinated water. The processes andmethods may further include removing at least a portion of the aqueousphase from the two-phase condensate to recover desalinated water. Themethods and processes of the present disclosure may further includesubjecting a distillation bottoms liquid to crystallization to separatethe distillation bottoms liquid into a salt product and a brinecomposition.

Referring to FIG. 1, a system for conducting the method of the presentdisclosure is schematically depicted and is generally associated withreference number 100. The system 100 for desalinating an aqueouscomposition 102 includes a distillation system 110 that may include adistillation vessel 112 in thermal communication with a heat source 116and a condenser 130 in fluid communication with the distillation vessel112. The system 100 further includes a condensate receiver 140 in fluidcommunication with the condenser 130. The condensate receiver 140 may beoperable to receive a multi-phase condensate 132 that includes at leasttwo liquid phases from the distillation system 110, the at least twoliquid phases comprising two or more liquid phases that are immisciblewith each other. The condensate receiver 140 may include a separationsystem operable to separate an aqueous phase 142 from the multi-phasecondensate 132 to produce a desalinated water stream 146. The system 100may also include a crystallization process 160 in fluid communicationwith the distillation vessel 112. The crystallization process 160 may beoperable to receive a distillation bottoms liquid 124 from thedistillation vessel 112 and separate at least a portion of a salt in thedistillation bottoms liquid 124 to produce a salt product 170 and abrine composition 172.

The systems and methods of the present disclosure may provide a processfor continuous desalination of aqueous streams and compositions thatinclude salts and may include organic constituents without experiencingfouling and the need for a periodic cleaning sequence, such as cleaningsequences required for operation of filtration and membrane-basedtechnologies. The systems and methods of the present disclosure alsoresult in reduced maintenance downtime caused by fouling of equipmentand membranes by oily residues or other organic constituents of theaqueous compositions. The systems and methods also do not requirepre-treatment processes to remove hydrogen sulfide (H₂S), oil droplets,or other organic constituents (such as organic acids, alcohols, phenols,dissolved C₁ to C₇ hydrocarbons, benzene, ethylbenzene, toluene, andxylenes for example) compared to membrane-based processes or thermalnon-azeotropic distillation processes. The systems and methods of thepresent disclosure may enable reduced energy consumption and morecompact equipment compared to other known thermal desalinationprocesses. The systems and methods of the present disclosure may alsoreduce the rate of corrosion of process equipment compared to otherknown thermal desalination processes because of the lesser temperatureat which hetero-azeotropic distillation is conducted compared to thetemperatures of the other thermal desalination processes. The systemsand methods of the present disclosure are designed for use inoxygen-free environments and with pressurized vessels and can be easilyintegrated into existing petroleum drilling, production, and refiningfacilities compared to currently available desalination technologies.However, the system and methods of the present disclosure can also beoperated at atmospheric pressure or under vacuum depending on theprocess conditions. The systems and methods of the present disclosuremay also produce oxygen-free desalinated water without the need for anextra step of adding an oxygen scavenger in the overall water treatmentprocess for several applications in the oil production and refiningindustry.

The formation of a hetero-azeotrope mixture that includes the aqueouscomposition and at least one entrainer reduces the boiling temperatureof the aqueous composition, which also reduces the distillationtemperature of the hetero-azeotropic distillation process compared toconventional thermal distillation. The decreased distillationtemperature of the hetero-azeotrope mixture, compared to conventionalthermal distillation, may reduce the energy required for distillationcompared to conventional thermal distillation and may allow the use ofwaste heat, which may be readily available at most oil and gas drilling,production, or refining facilities, or other renewable energy sources,such as solar, wind, or other renewable energy sources. Thus, thesystems and method of the present disclosure may have lesser operatingcosts compared to non-azeotropic thermal distillation processes andother desalination processes, such as membrane processes,electro-dialysis, ion exchange, or thin film evaporation, for example.The systems and methods of the present disclosure may also provide theability to process greater quantities of the aqueous compositions perpass, potentially decreasing the capital expense compared to currentlyavailable technologies.

As used in this disclosure, the term “produced water” refers to aqueousstreams that are extracted from subterranean formations by productionwells during petroleum or natural gas production or aqueous streamsgenerated from gas and oil separation plants (GOSP) or other petroleumprocessing facilities. Subterranean oil and gas reserves may ofteninclude substantial amounts of water along with the oil and gas. Duringgas and oil extraction, this water is also extracted as a by-productalong with the gas or oil and is subsequently separated from the gas oroil. This water separated from the gas and oil may also be referred toas produced water. Produced water may include water naturally occurringin the subterranean formation, water injected into the subterraneanformation to force oil and gas in the subterranean formation towards theproduction well, other water extracted from the subterranean formation,or combinations of these. As previously discussed, produced water mayalso include water streams from petroleum operations such as the GOSPand petroleum processing facilities. Produced water may also include amixture of water extracted from a subterranean formation and one or moreother streams of water, such as fresh water used for crude oildesalting, industrial wastewater generated at another petroleumprocessing facility, water from firefighting water storage, other waterstream, or combinations of these.

As used in this disclosure, the term “distillation” may refer to aprocess of separating one or more constituents from a liquid compositionbased on differences in boiling temperatures of the constituents of theliquid composition.

As used in this disclosure, the term “azeotrope” may refer to a mixtureof two liquid components in which the relative concentration between thetwo liquid components cannot be changed through distillation.Distillation of an azeotrope results in a vapor phase that has the samerelative concentrations of the two components in the liquid phase.

As used in this disclosure, the term “hetero-azeotrope” may refer to anazeotrope in which the two liquid components are considered to beimmiscible, which results in the hetero-azeotrope mixture being amulti-phase liquid. Two liquid components may be considered to beimmiscible if a mixture of the two liquid components results in atwo-phase liquid.

As used in this disclosure, the term “salinity” may refer to theconcentration of dissolved salts in a liquid and is reported in thisdisclosure in units of grams per liter (g/L).

As used in this disclosure, the term “ambient temperature and pressure”refers generally to a temperature of 25° C. and atmospheric pressure atsea level (1 atmosphere=101.3 kilopascals (kPa)).

Referring now to FIG. 1, the process for desalinating the aqueouscomposition will be generally described in the context of system 100.The process for desalinating the aqueous composition 102 using system100 of FIG. 1 includes forming a hetero-azeotrope mixture 122 bycombining the aqueous composition 102 with at least one entrainer 120.The hetero-azeotrope mixture 122 is then subjected to ahetero-azeotropic distillation process in the distillation system 110.Hetero-azeotropic distillation of the hetero-azeotrope mixture 122 mayproduce a multi-phase condensate 132 that includes at least an aqueousphase 142 and an entrainer-rich phase 144. The aqueous phase 142includes the desalinated water, which may be drawn out of the condensatereceiver 140 in a desalinated water stream 146. Hetero-azeotropicdistillation of the hetero-azeotrope mixture 122 may additionallyproduce a distillation bottoms liquid 124, which may have an increasedsalinity (increased salt concentration) compared to the hetero-azeotropemixture 122. The multi-phase condensate 132 may be passed from thecondenser 130 of the distillation system 110 to the condensate receiver140, which may be operable to separate the aqueous phase 142 (or atleast a portion of the aqueous phase 142), the entrainer-rich phase 144(or at least a portion of the entrainer-rich phase 144), or both fromthe multi-phase condensate 132. The distillation bottoms liquid 124 maybe passed to the crystallizer 160. The distillation bottoms liquid 124may be subjected to crystallization in the crystallizer 160, whichresults in separation of the bottoms liquid 124 into the salt product170 and the brine composition 172. The systems and methods fordesalinating the aqueous compositions 102 will now be described infurther detail.

The aqueous composition 102 includes water and at least one salt. Insome embodiments, the aqueous composition 102 may have a plurality ofdifferent salts resulting in a plurality of ionic species in the aqueouscomposition 102. For example, the salts in the aqueous composition 102may include but are not limited to chloride, bromide, fluoride, sulfide,sulfate, carbonate, phosphate, nitrate, or nitrite salts of calcium,sodium, potassium, magnesium, other cationic species, or combinations ofthese. The aqueous composition 102 may include produced water, waterstreams from oil-desalting, other aqueous streams from oil refiningoperations, seawater, briny water, salty wastewater, briny groundwater,the brine composition 172 from crystallization of the distillationbottoms liquid 124 (subsequently described in this disclosure), otheraqueous compositions having at least one salt, or combinations of these.In some embodiments, the aqueous composition 102 may be briny water. Asused in this disclosure, the term “briny water” may refer to waterhaving a salinity of greater than or equal to 1 gram per liter (g/L),such as in a range of from 3 g/L to 300 g/L. In some embodiments, theaqueous composition 102 may be produced water from hydrocarbon drilling,production, or refining operations. In some embodiments, the aqueouscomposition 102 may be seawater or salty wastewater.

The aqueous compositions 102 may have a salinity that is sufficient tomake the aqueous composition 102 unsuitable for use in petroleumdrilling, production, or refining operations, such as preparation ofdrilling fluids, oil desalting, or other processes. The aqueouscomposition 102 may have salinity sufficient to make the aqueouscomposition 102 unsuitable for anthropologic or agricultural uses. Theaqueous composition 102 may have salinity of greater than or equal to 1g/L, greater than or equal to 10 g/L, greater than or equal to 20 g/L,greater than or equal to 100 g/L, or even greater than or equal to 200g/L at ambient temperature and pressure. The aqueous composition 102 mayhave a salinity of less than or equal to 360 g/L, less than or equal to350 g/L, less than or equal to 300 g/L, or even less than or equal to200 g/L at ambient temperature and pressure. In some embodiments, theaqueous composition 102 may have salinity less than the solubility limitof the salts in water. The solubility limit is the concentration atwhich solids, such as salts, will start to precipitate, which is about360 g/L for salts in water at ambient temperature and pressure. For morecomplex solutions, such as produced water that includes salts, organics,oil residues, and other constituents, the solubility limit may be about350 g/L. In some embodiments, the aqueous composition 102 may have asalinity of from 1 g/L to 360 g/L, from 1 g/L to 350 g/L, from 1 g/L to300 g/L, from 1 g/L to 200 g/L, from 10 g/L to 360 g/L, from 10 g/L to350 g/L, from 10 g/L to 300 g/L, from 20 g/L to 360 g/L, from 20 g/L to350 g/L, from 20 g/L to 300, from 200 g/L to 360 g/L, from 200 g/L to350 g/L, or even from 200 g/L to 300 g/L at ambient temperature andpressure. In some embodiments, the aqueous composition 102 may be agreater-salinity aqueous composition having salinity of greater than orequal to 200 g/L at ambient temperature and pressure. Alternatively, inother embodiments, the aqueous composition 102 may be a lesser-salinityaqueous composition having a salinity of less than 200 g/L at ambienttemperature and pressure.

The salinity of the aqueous composition 102 may cause the aqueouscomposition 102 to have a boiling temperature of greater than 100degrees Celsius (° C.) at atmospheric pressure. The boiling temperatureof the aqueous composition 102 may be greater than 101° C., greater than102° C., or even greater than or equal to 105° C. Generally, the boilingtemperature of the aqueous composition 102 increases with increasingsalinity.

The aqueous composition 102 may also include organic compounds, such asfree oil and hydrocarbon gases, dissolved hydrocarbons (such asdissolved C₁ to C₇ hydrocarbons), other dissolved organic compounds,such as phenolic compounds, organic acids, alcohols, benzene,ethylbenzene, toluene, xylenes, other organic compounds, or combinationsof these. The aqueous composition 102 may have an oil content of greaterthan 0.1 weight percent (wt. %) based on the total weight of the aqueouscomposition 102. In some embodiments, the aqueous composition 102 mayhave up to or greater than 1 wt. % oil. The oil may be present in theaqueous composition 102 in the form of oil droplets suspended in theaqueous composition. Other organic compounds that may be present in theaqueous composition 102 may include, but are not limited to, phenoliccompounds, alkanes, alkenes, organic acids, alcohols, waxes,asphaltenes, aromatic compounds, or combinations of these.

Some aqueous compositions 102, such as aqueous compositions 102comprising produced water, may include inorganic contaminants, such asdissolved minerals, metals, and anionic species. Inorganic contaminantsthat may be present in the produced water may include, but are notlimited to, aluminum, calcium, magnesium, arsenic, cadmium, chromium,copper, iron, lead, manganese, nickel, potassium, sodium, selenium,zinc, barium, lithium, sulfur, strontium, titanium, vanadium, othermetal or inorganic contaminant, or combinations of these. The aqueouscomposition 102 may also include water-soluble polymers from theformulation of oilfield chemicals, such as demulsifiers, hydrateinhibitors, drilling fluids, spacer fluids, or other chemicals. Examplesof these water-soluble polymers may include, but are not limited to,polyethylene oxides from demulsifier makeup, polyamides found in hydrateinhibitors, xanthan gum (XC) polymers used in drilling fluids, otherwater-soluble polymers, or combinations of polymers.

As previously discussed, the aqueous composition 102 is combined with atleast one entrainer 120 to form the hetero-azeotrope mixture 122 thathas a lesser boiling temperature compared to the boiling temperature ofthe aqueous composition 102 without the entrainer 120. In some cases,only a portion of the aqueous composition 102 may be combined with theentrainer 120 to form the hetero-azeotrope mixture 122, such as when thesalinity of the aqueous composition 102 is greater than 200 g/mL and aportion of the salt is removed from the aqueous composition 102 prior toforming the hetero-azeotrope mixture 122. The entrainer 120 (orentrainers) forms an azeotrope with the water of the aqueous composition102. Not intending to be bound by any particular theory, it is believedthat the water molecules of the aqueous composition 102 interact withthe molecules of the entrainer 120 to form a complex, which exhibitdistinct physical and chemical properties. If the interaction betweenthe water molecules and the entrainer is strong, then the azeotropeforms a homogeneous mixture. When the interaction between the watermolecules and entrainer molecules is weaker, a hetero-azeotrope may beformed in which the vapor phase co-exists with two separate liquidphases, an aqueous phase and an entrainer phase.

Referring to FIG. 2, a phase equilibrium diagram for a binary mixture of1-butanol and water is depicted at ambient pressure. The phaseequilibrium diagram of FIG. 2 graphically depicts the boiling pointcurve 1002, which is the boiling temperature (y-axis) as a function ofthe mass fraction of water in the liquid (x-axis), and the dew pointcurve 1004, which is the dew point temperature (y-axis) as a function ofthe mass fraction of water in the vapor phase (x-axis). At the azeotropepoint 1006, the boiling temperature and dew point temperature converge,and the composition of the vapor phase is the same as the composition ofthe liquid phase. At the azeotrope composition and temperature, thecomposition (mixture of 1-butanol and water) boils at constanttemperature to produce the vapor phase that has the same relativecomposition as the liquid phase. When the mass fraction of water in themixture is less than the azeotrope composition, the vapor phase may havea greater concentration of 1-butanol than the vapor phase at theazeotrope composition. Thus, the 1-butanol may be transitioned to thevapor phase at a greater rate than the water, thus, increasing the massfraction of water in the mixture. The mass fraction of water in themixture may increase until the composition of the mixture reaches theazeotrope point 1006, where the composition of the vapor phase is thesame as the liquid phase, which results in the boiling temperature andcomposition of the liquid phase remaining constant.

FIG. 2 also depicts the immiscibility range 1008 between the water and1-butanol. At compositions within the immiscibility range 1008, themixture of 1-butanol and water form a two-phase liquid. As shown in FIG.2, the azeotrope point 1006 of a mixture of 1-butanol and water has anazeotrope composition that is within the immiscibility range of1-butanol and water. Thus, 1-butanol and water may form ahetero-azeotrope mixture that includes a multiple-phase liquid.

This azeotrope point 1006, which has a boiling temperature of thehetero-azeotrope for a distinct mass fraction of water, is a physicalattribute of the hetero-azeotrope mixture 122. At a given pressure, eachhetero-azeotrope combination may have an azeotrope point 1006characterized by a hetero-azeotrope boiling temperature and ahetero-azeotrope composition, which may be expressed as a mass fractionof one or more constituents in the vapor phase or liquid phase.Referring now to FIG. 3, the hetero-azeotrope composition (mass fractionof water in the vapor phase) (y-axis) and the hetero-azeotrope boilingtemperature (x-axis) for a plurality of different binaryhetero-azeotrope pairs formed with water and a plurality of differententrainer compounds are graphically depicted. As shown in FIG. 3,hetero-azeotropes having a greater hetero-azeotrope boiling temperaturegenerally have a hetero-azeotrope composition with a greaterconcentration of water compared to hetero-azeotropes having lesserhetero-azeotrope boiling temperatures. As shown in FIG. 3, selection ofthe entrainer used to form the hetero-azeotrope mixture 122 mayinfluence the energy consumption of the desalination process of thepresent disclosure by fixing the distillation temperature at theconstant hetero-azeotrope boiling temperature and may also influence theproduction rate of desalinated water by setting the concentration ofwater in the vapor phase resulting from the distillation.

The entrainer 120 may be an organic compound capable of forming ahetero-azeotrope mixture when combined with the aqueous composition 102.The entrainer 120 may have an entrainer boiling temperature that is lessthan the boiling temperature of the aqueous composition 102. Forinstance, the entrainer 120 may have an entrainer boiling temperature ofless than or equal to 120° C., less than or equal to 100° C., less thanor equal to 90° C., less than or equal to 80° C., or even less than orequal to 70° C. Entrainers 120 suitable for forming the hetero-azeotropemixture 122 may be considered to be immiscible with water. For instance,the entrainers 120 may have a solubility in water of less than 20 gramsper 100 grams of water (g/100 g water), such as less than 10 g/100 gwater. Or even less than 1 g/100 g water at 25° C. and atmosphericpressure. In some embodiments, the entrainers 120 may have a solubilityin water of from 7×10⁻³ g/100 g water to 20 g/100 g water, from 7×10⁻³g/100 g water to 10 g/100 g water, from 7×10⁻³ g/100 g water to 1 g/100g water, from 0.01 g/100 g water to 20 g/100 g/100 g water, from 0.01g/100 g water to 10 g/100 g water, or from 0.01 g/100 g water to 1 g/100g water, the solubility being measured at 25° C. and atmosphericpressure. The entrainers 120 may be selected to form an azeotrope withthe aqueous composition 102 in which the azeotrope composition at theazeotrope temperature and the operating pressure of the distillationsystem 110 is within an immiscibility range of a mixture of theentrainer 120 and the aqueous composition 102.

The entrainers 120 may be chemically stable when combined with theaqueous composition 102. As used in this disclosure, the term“chemically stable” means that the entrainer does not undergo a chemicalreaction to form another species when contacted with one or more of theconstituents of the aqueous composition 102. The entrainers 120 may havereduced or negligible reactivity with water and the other constituentsof the aqueous composition 102. Reaction of the entrainer 120 with wateror other constituents of the aqueous composition 102 may result in lossof the entrainer 120 due to consumption of the entrainer 120 by thereaction or production of toxic compounds or compounds that arehazardous in an oil and gas processing environment. The entrainers 120may not include compounds that are highly-toxic or are incompatible withoil and gas environments, such as compounds that undergo side reactionswith acid gases or crude oil droplets in the aqueous composition 102.The entrainer 120 may not include halogen-containing compounds, amines,nitriles, acetals, aldehydes, vinyl ethers, or combinations of these. Insome embodiments, the entrainer 120 may be substantially free ofhalogen-containing compounds, amines, nitriles, acetals, aldehydes,vinyl ethers, or combinations of these. As used in this disclosure, theterm “substantially free” of a component means less than 1 wt. % of thatcomponent in a composition, reactor, vessel, or stream. For example, anentrainer 120 that is substantially free of halogens, amines, nitriles,acetals, aldehydes, vinyl ethers, or combinations of these may have lessthan 1 wt. % halogens, amines, nitriles, acetals, aldehydes, vinylethers, or combinations of these based on the total weight of theentrainer 120.

The entrainer may not include halogen compounds (compounds containing ahalogen atom) because halogens may decompose into alcohol in thepresence of water in acidic or basic conditions. The aqueous composition102 may contain hydrogen sulfide which may decompose halogen-containingentrainers into thiols or thioethers. Entrainers containing amine(s) mayreact readily with dissolved carbon dioxide and hydrogen sulfide in theaqueous composition 102 to form ammonium salts or carbamates, whichwould then dissolve in the briny water of the aqueous composition 102.Entrainers containing nitrile(s) may decompose thermally by releasingtrace amounts of cyanic acid, which is highly toxic, or chemically byreacting with hydrogen sulfide to yield thioamides. Entrainerscontaining acetal(s) may decompose to the corresponding aldehydes andalcohols. The aldehydes may subsequently decompose into the acids withthe presence of oxygen in the water or into aldehyde hydrates, alsoknown as gem-diols, which are soluble in water. Thus, the use of acetalor aldehyde containing entrainers would result in loss of the entrainerthrough side reactions and solubility in the water and possibleintroduction of free oxygen into the various streams. Entrainerscontaining vinyl ether(s) may hydrolyze with the residual acidity of thewater into the corresponding aldehyde(s) and alcohols (or acid). Thus,entrainers containing halogens, amines, nitriles, vinyl ethers, acetals,aldehydes or a combination of these functionalities may be unsuitablefor use as the entrainer in the methods and processes for desalinatingaqueous compositions 102 of the present disclosure.

The entrainer 120 may include one or more than one chemicalfunctionality selected from an alkane, an alkene, an aromatic, an ester,an alcohol, a thiol, a disulfide, a sulfide, an ether, a ketone, a nitrogroup, or combinations of these. The entrainer 120 may be selected from2-methyl-1,3-butadiene; pentane; 2-methyl-2-butene;methylenecyclobutane; carbon disulfide; 1-hexene; ethyl formate;4-methyl-2-pentene; 3-methyl-3-buten-1-ol; hexane; isopropyl ether;cis-1-butenyl ethyl ether; 1-butenyl methyl ether; benzene; cyclohexane;ethyl acetate; cyclohexene; methyl propanoate; propyl formate; isopropylacetate; ethylbutyl ether; isopropylacetate; butyl ethyl ether;1-heptene; 2,5-dimethylfuran; 2,2,4-trimethylpentane; heptane; isobutylformate; methylisopropenyl ketone; diisobutylene; propyl acetate;3-pentanone; allyl acetate; nitroethane; 2,6-dimethyl-4-heptanol;toluene; 1,2-propanediol diacetate; butyl isopropenyl ether;2-methyl-2-butanol; methylisobutyl ketone; isobutyl acetate;2-methylpropyl acetate; cyclopropyl methyl ketone; propyl propanoate;octane; isobutyl alcohol; 2-pentanol, or combinations of theseentrainers. Table 1 provides the azeotropic temperature, azeotropicpressure, and the mass fraction of water in the vapor phase forhetero-azeotrope mixtures that include water and each of the previouslyrecited entrainer compounds. The entrainer compounds as well as thehetero-azeotrope boiling temperature and mass fraction of water in thehetero-azeotrope vapor are provided in Table 1.

TABLE 1 Hetero-Azeotrope Boiling Temperatures and Mass Fraction of Waterin the Vapor for Exemplary Entrainer Compounds Hetero- Hetero- MassAzeotrope Azeotrope Fraction of Entrainer Boiling Temp. Pressure Waterin Compound (° C.) (kPa) Vapor 2-Methyl-1,3-butadiene 32.7 101.330.014287 Pentane 34.6 — 0.014 2-Methyl-2-butene 36.6 101.33 0.01753Methylenecyclobutane 40.0 101.33 0.005691 Carbon disulfide 43.6 — 0.021-Hexene 45.0  63.35 0.0366 Ethyl formate 52.6 — 0.05 Ethylformate 52.6101.33 0.017961 4-Methyl-2-pentene 53.3 — 0.035 3-Methyl-3-buten-1-ol60.00 101.33 0.5788 Hexane 61.6 101.33 0.052903 Isopropyl ether 62.2 —0.046 Cis-1-Butenyl ethyl ether 64.0 — 0.061 1-Butenyl methyl ether 67.0— 0.072 Benzene 69.2 101.33 0.089107 Benzene 69.4 — 0.089 cyclohexane69.8 — 0.085 Ethyl acetate 70.4 — 0.081 Ethyl acetate 70.4 101.330.080152 Cyclohexene 70.8 101.33 0.089245 Methyl propanoate 71.6 101.330.08228 Propyl formate 71.7 101.33 0.083711 Isopropyl acetate 75.9 —0.111 Ethylbutyl ether 76.6 — 0.119 Isopropylacetate 76.6 101.330.103583 Butyl ethyl ether 76.7 101.33 0.107913 1-Heptene 77.05 101.330.1130 2,5-Dimethylfuran 77.0 — 0.117 1-Heptene 77.05 101.33 0.1132,2,4-Trimethylpentane 78.8 101.33 0.110968 Heptane 79.2 — 0.129 Heptane79.2 101.33 0.128585 Isobutylformate 79.6 101.33 0.124254Methylisopropenyl ketone 81.5 — 0.184 Diisobutylene 82.0 — 0.12 Propylacetate 82.76 101.33 0.161837 3-Pentanone 82.9 101.33 0.15901 Allylacetate 83.0 — 0.167 Nitroethane 83.75 101.33 0.203587 Methylpropylketone 83.8 — 0.196 Butyl formate 83.8 101.33 0.1691512,6-Dimethyl-4-heptanol 83.9 — 0.143 Toluene 84.1 101.33 0.176408Toluene 85.0 — 0.202 1,2-Propanediol diacetate 85.0  59.41 0.80806 ButylIsopropenyl ether 86.3 — 0.188 2-Methyl-2-butanol 87.7 101.75 0.262545Methylisobutyl ketone 87.9 — 0.24 Isobutyl acetate 87.9 101.33 0.2189442-Methylpropyl acetate 88.4 — 0.22 Cyclopropyl methyl ketone 88.5 101.190.339435 Propyl propanoate 88.9 101.33 0.231244 Octane 89.6 101.330.255214 Isobutyl alcohol 89.7 — 0.3 2-Pentanol 90.0  92.49 0.38623 Thedata in Table 1 was obtained from J. Gmehling, J Menke, J. Krafczyk, K.Fischer, J. -C, Fontaine, and H. V. Kehianian, “Azeotropic Data forBinary Mixtures,” CRC Handbook of Chemistry and Physics, 92nd Edition(2011) pp. 6-210 to 6-228.

As shown in Table 1, the mass fraction of water in the hetero-azeotropevapor increases with increasing hetero-azeotrope boiling temperature.

The hetero-azeotrope mixture 122 may comprise, consist of, or consistessentially of the aqueous composition 102 and one or more entrainers120. The hetero-azeotrope mixture 122 may include an amount of theentrainer 120 sufficient to form the hetero-azeotrope with the aqueouscomposition 102. The hetero-azeotrope mixture 122 may have from 10volume percent (vol. %) to 95 vol. %, from 10 vol. % to 80 vol. %, from40 vol. % to 95 vol. %, from 40 vol. % to 80 vol. %, from 60 vol. % to95 vol. %, or from 60 vol. % to 80 vol. % aqueous composition 102 basedon the total volume of the hetero-azeotrope mixture 122. A volume ratioof the aqueous composition 102 to the entrainers 120 may be defined asthe volume percent of the aqueous composition 102 in thehetero-azeotrope mixture 122 divided by the total volume percent of allof the entrainers 120 in the hetero-azeotrope mixture 122. Thehetero-azeotrope mixture 122 may have a volume ratio of the aqueouscomposition 102 to the entrainers 120 sufficient to form thehetero-azeotrope. For instance, the hetero-azeotrope mixture 122 mayhave a volume ratio of the aqueous composition 102 to the entrainers 120of from 0.2 to 9.0, from 0.2 to 4.0, from 0.2 to 1.5, from 0.2 to 1.0,from 0.2 to 0.8, from 0.2 to 0.6, from 0.4 to 9.0, from 0.4 to 4.0, from0.4 to 1.5, from 0.4 to 1.0, from 0.4 to 0.8, from 0.4 to 0.6, from 0.6to 9.0, from 0.6 to 4.0, from 0.6 to 1.5, from 0.6 to 1.0, from 0.6 to0.8, from 0.8 to 9.0, from 0.8 to 4.0, from 0.8 to 1.5, from 0.8 to 1.0,from 1.0 to 9.0, from 1.0 to 4.0, from 1.0 to 1.5, from 1.5 to 9.0, orfrom 1.5 to 4.0.

As previously discussed, the hetero-azeotrope boiling temperature of thehetero-azeotrope mixture 122 is a physical constant at a given pressureand sets the operating distillation temperature in the distillationsystem 110 at the operating distillation pressure. As used in thisdisclosure, the operating distillation pressure refers to the pressurein the distillation system 110 during operation of the distillationsystem 110. The hetero-azeotrope mixture 122 may have a hetero-azeotropeboiling temperature that is less than the boiling temperature of theaqueous composition 102 at the operating distillation pressure of thedistillation system 110. The hetero-azeotrope mixture 122 having ahetero-azeotrope boiling temperature less than the boiling temperatureof the aqueous composition 102 at the operating distillation pressuremay enable the distillation to be carried out on the hetero-azeotropemixture 122 with less energy compared to subjecting the aqueouscomposition 102 to conventional thermal distillation. In someembodiments, the hetero-azeotrope mixture 122 may have ahetero-azeotrope boiling temperature at the operating distillationpressure that is less than the boiling temperature of the aqueouscomposition 102 and the boiling temperature of the entrainer 120 at theoperating distillation pressure. In some embodiments, thehetero-azeotrope mixture 122 may have a hetero-azeotrope boilingtemperature at an operating distillation pressure equal to atmosphericpressure at sea level (101.325 kilopascals (kPa)) of less than or equalto 100° C., such as less than or equal to 95° C., less than or equal to90° C., less than or equal to 85° C., or even less than or equal to 80°C. For instance, the hetero-azeotrope mixture 122 may have ahetero-azeotrope boiling temperature of from 40° C. to 100° C., from 50°C. to 95° C., from 50° C. to 90° C., from 50° C. to 85° C., from 50° C.to 80° C., from 60° C. to 95° C., from 60° C. to 90° C., from 60° C. to85° C., or from 60° C. to 80° C. at an operating distillation pressureof 101.325 kPa. The hetero-azeotrope boiling temperature may increasewith increasing pressure, such as increasing operating distillationpressure. Additionally, increasing the pressure may also change theratio of water to entrainer in the hetero-azeotrope mixture 122. Forexample, increasing the pressure may result in an increase in the volumepercent (as well as mole percent and mass percent) of water in thehetero-azeotrope at the hetero-azeotrope composition. Thus, increasingthe operating distillation pressure can increase the proportion ofdesalinated water in the vapor phase during distillation of thehetero-azeotrope mixture 122.

The hetero-azeotrope mixture 122 may be a ternary hetero-azeotrope inwhich the aqueous composition 102 is combined with two entrainers, suchas a first entrainer and a second entrainer. Formation of a ternaryhetero-azeotrope mixture may enable the distillation temperature in thedistillation system 110 to be further adjusted to a temperature that isin-between a first hetero-azeotrope boiling temperature and a secondhetero-azeotrope boiling temperature. The first hetero-azeotrope boilingtemperature is the hetero-azeotrope boiling temperature of a firsthetero-azeotrope comprising the aqueous composition 102 and the firstentrainer with the concentration of the second entrainer equal to zero,and the second hetero-azeotrope boiling temperature is ahetero-azeotrope boiling temperature of a second hetero-azeotropecomprising the aqueous composition 102 and the second entrainer with theconcentration of the first entrainer equal to zero. The boilingtemperature of the hetero-azeotrope mixture that includes a ternaryazeotrope may be increased or decreased by increasing or decreasing theconcentration of the first entrainer, the second entrainer or both. Insome cases, the hetero-azeotrope mixture 122 may be amulti-heteroazeotrope that includes 2, 3, 4, or more than 4 entrainers.

Referring to FIGS. 4A and 4B, ternary phase equilibria diagrams for aternary hetero-azeotrope formed from water, benzene, and toluene. Theternary phase equilibria diagrams were generated using Aspen Plus v9modeling software. FIG. 4A represents the ternary phase equilibria at 1bar (100 kilopascals (kPa), where 1 bar is equal to 100 kPa) ofpressure, and FIG. 4B represents the ternary phase equilibria at apressure of 3.5 bars (350 kPa) of pressure. Referring to FIG. 4A, at 1bar, a first hetero-azeotrope boiling temperature of a firsthetero-azeotrope comprising water and benzene occurs at 68.66° C. atpoint 1022 in FIG. 4, and a second hetero-azeotrope boiling temperatureof a second hetero-azeotrope comprising water and toluene occurs at83.81° C. at point 1024. Formation of a ternary hetero-azeotrope thatincludes water, toluene, and benzene may allow the boiling temperatureto be adjusted within a range between the first hetero-azeotrope boilingtemperature (68.66° C.) and the second hetero-azeotrope boilingtemperature (83.81° C.). The line 1020 in FIG. 4A between point 1022 andpoint 1024 represents the range of the ternary hetero-azeotropecompositions having ternary hetero-azeotrope boiling temperaturesbetween the first hetero-azeotrope boiling temperature and the secondhetero-azeotrope boiling temperature. Thus, use of a ternaryhetero-azeotrope that includes water, benzene, and toluene may enablethe distillation temperature of the distillation system 110 to be variedwithin a range of from 68.66° C. and 83.81° C. at a pressure of 100 kPa.

Increasing the pressure may result in an increase in thehetero-azeotrope boiling temperature of the hetero-azeotrope mixture 122and may also slightly change the composition of the hetero-azeotrope.Referring to FIG. 4B, the ternary phase equilibrium diagram for a water,toluene, and benzene mixture at 350 kPa is depicted. As shown by FIG.4B, for the water, toluene, and benzene ternary hetero-azeotrope,increasing the pressure increases the first hetero-azeotrope boilingtemperature at point 1032 to 106.78° C. and the second hetero-azeotropemixture at point 1034 to 121.28° C. Thus, the range of hetero-azeotropeboiling temperatures for the water/benzene/toluene ternary mixtureincreases by about 40° C. for an increase of 250 kPa (comparing FIGS. 4Aand 4B). Additionally, the increase in pressure shifts the range ofternary hetero-azeotrope compositions (lines 1020 and 1030) towardsgreater molar concentration of water. For the water/benzene/tolueneternary hetero-azeotrope mixture of FIGS. 4A and 4B, the composition ofthe ternary hetero-azeotrope increases in water by 5 mole percent (mol%) and decreases in benzene by approximately 10 mol % in response to anincrease in pressure of 250 kPa. Thus, FIG. 4A and FIG. 4B show thatincreasing the pressure can increase the proportion of water in theternary hetero-azeotrope, and thus the amount of water in the vaporphase. However, increasing the pressure also increases the ternaryhetero-azeotrope boiling temperature, which may increase the energyinput into the distillation system 110.

Referring to FIG. 5, a ternary hetero-azeotrope may also be formed fromthe combination of water with benzene and n-pentane as the entrainers.At 3.5 bar (350 kPa), the first hetero-azeotrope boiling temperature ofthe first hetero-azeotrope comprising water and n-pentane occurs at73.43° C. at point 1042 in FIG. 5, and the second hetero-azeotropeboiling temperature of the second hetero-azeotrope comprising water andbenzene occurs at 106.78° C. at point 1044. In FIG. 5, the line 1040between point 1042 and point 1044 represents the range of the ternaryhetero-azeotrope compositions of water, benzene, and n-pentane havingternary hetero-azeotrope boiling temperatures between the firsthetero-azeotrope boiling temperature and the second hetero-azeotropeboiling temperature. With a ternary hetero-azeotrope formed from water,benzene, and n-pentane, the distillation temperature may be variedwithin a range of from 73.43° C. to 106.78° C. at 350 kPa.

Referring to FIG. 6, a ternary hetero-azeotrope may be formed from thecombination of water with toluene and n-pentane as the entrainers. At3.5 bar (350 kPa), the first hetero-azeotrope boiling temperature of thefirst hetero-azeotrope comprising water and n-pentane occurs at 72.41°C. at point 1052 in FIG. 6, and the second hetero-azeotrope boilingtemperature of the second hetero-azeotrope comprising water and tolueneoccurs at 120.32° C. at point 1054. In FIG. 6, the line 1050 betweenpoint 1052 and point 1054 represents the range of the ternaryhetero-azeotrope compositions of water, toluene, and n-pentane havingternary hetero-azeotrope boiling temperatures between the firsthetero-azeotrope boiling temperature and the second hetero-azeotropeboiling temperature. With a ternary hetero-azeotrope formed from water,toluene, and n-pentane, the distillation temperature may be variedwithin a range of from 72.41° C. to 120.32° C. at 350 kPa. Althoughdescribed in relation to water/benzene/toluene, water/benzene/n-pentane,and water/toluene/n-pentane ternary hetero-azeotropes, it is understoodthat other combinations of entrainers may provide a ternaryhetero-azeotrope with the aqueous composition and the present disclosureis not intended to be limited to the specific ternary hetero-azeotropecombinations specifically recited.

The hetero-azeotrope mixture 122 may be formed by combining the aqueouscomposition 102 with the entrainers 120. In some embodiments, theaqueous composition 102 may be combined with the entrainers 120 to formthe hetero-azeotrope mixture 122 in the distillation system 110.Referring to FIG. 1, the aqueous composition 102 may be combined withthe entrainers 120 in the distillation vessel 112 of the distillationsystem 110. As shown in FIG. 1, the distillation vessel 112 of thedistillation system 110 may include an aqueous composition inlet 126 anda make-up entrainer inlet 128. The aqueous composition 102 may besupplied to the distillation vessel 112 through the aqueous compositioninlet 126. The entrainers 120 may also be provided to the distillationvessel 112 by entrainer recycle stream 148, which recycles theentrainers 120 from the condensate receiver 140, with additional make-upentrainer 121 added from the make-up entrainer inlet 128. Thehetero-azeotrope mixture 122 may be a multi-phase mixture in thedistillation vessel 112 of the distillation system. Alternatively oradditionally, the aqueous composition 102 and the entrainer 120 may becombined to form the hetero-azeotrope mixture 122 upstream of thedistillation system 110, such as in a pre-mix vessel (not shown) orother preliminary process, such as the feedstream crystallizer 312,which will be described subsequently in this disclosure in reference toFIG. 10.

Referring again to FIG. 1, desalinated water may be separated from thehetero-azeotrope mixture 122 through hetero-azeotropic distillation inthe distillation system 110. The hetero-azeotrope mixture 122 may besubjected to distillation in the distillation system 110, which resultsin separation of the hetero-azeotrope mixture 122 into the multi-phasecondensate 132 and the distillation bottoms liquid 124. As previouslydiscussed, the hetero-azeotrope mixture 122 may have a hetero-azeotropeboiling temperature which is a fixed physical constant at a givenpressure based on the composition of the hetero-azeotrope mixture 122,such as the type of entrainer(s) 120 used or the proportions ofcomponents of a ternary hetero-azeotrope. The hetero-azeotrope mixture122 may be subjected to distillation at a distillation temperature equalto the hetero-azeotrope boiling temperature of the hetero-azeotropemixture 122 at the operating distillation pressure. The hetero-azeotropemixture 122 may be subjected to distillation at a distillationtemperature that is less than or equal to the boiling temperature of theaqueous composition 102 (without the entrainer) at the operatingdistillation pressure of the distillation system 110. Thehetero-azeotrope mixture 122 may be subjected to distillation at adistillation temperature of less than or equal to 100° C., less than orequal to 95° C., less than or equal to 90° C., less than or equal to 85°C., or even less than or equal to 80° C. at the operating distillationpressure. In some embodiments, the hetero-azeotrope mixture 122 may besubjected to hetero-azeotropic distillation at a distillationtemperature of from 40° C. to 100° C., from 50° C. to 95° C., from 50°C. to 90° C., from 50° C. to 85° C., from 50° C. to 80° C., from 60° C.to 95° C., from 60° C. to 90° C., from 60° C. to 85° C., or from 60° C.to 80° C. at the operating distillation pressure. The distillationtemperature may vary depending on the operating distillation pressure ofthe distillation system 110.

The distillation of the hetero-azeotrope mixture 122 may be carried outat an operating distillation pressure sufficient for use in the oil andgas industry. The operating distillation pressure at which thehetero-azeotrope mixture 122 is subjected to distillation may be from100 kPa (1 bar) to 1000 kPa (10 bar), or from 350 kPa (3.5 bar) to 1000kPa (10 bar). The operating distillation pressure may be adjusted toincrease or decrease the hetero-azeotrope temperature andhetero-azeotrope composition of the hetero-azeotrope mixture 122. Forinstance, the distillation temperature may be increased or decreased byincreasing or decreasing the operating distillation pressure of thedistillation system 110. Increasing or decreasing the operatingdistillation pressure may also modify the hetero-azeotrope compositionof the hetero-azeotrope mixture 122, such as modifying the mass fractionof water in the vapor phase. As discussed in relation to FIG. 4B,increasing the operating distillation pressure may increase thehetero-azeotrope boiling temperature and may also increase the massfraction of water in the vapor phase during distillation. Thedistillation temperature may also be increased or decreased throughselection of the entrainer 120.

The distillation system 110 for subjecting the hetero-azeotrope mixture122 to hetero-azeotropic distillation may include a distillation vessel112, a heat source 116 in thermal communication with the distillationvessel 112, and a condenser 130 in fluid communication with a vaporspace 114 of the distillation vessel 112. The distillation vessel 112may be a pressure-vessel capable of withstanding the operatingdistillation pressures within the operating range of the distillationsystem 110, such as operating distillation pressures of from 100 kPa to1000 kPa. In some aspects, the distillation vessel 112 may be a flashpot fluidly coupled to the condenser 130. In some aspects, thedistillation vessel 112 may include a demister (not shown). The demistermay be used to reduce or prevent droplets of the liquid hetero-azeotropemixture 122, which may include the salts and other contaminants, frompropagating through the distillation system 110 to the condenser 130 toreduce or prevent passage of the salt and other contaminants throughinto the condensate receiver 140 and potentially contaminating thedesalinated water produced.

Referring to FIG. 7, the distillation system 110 may include thedistillation vessel 112 and at least one short-path distillation column190 in fluid communication with the vapor space 114 of the distillationvessel 112. The distillation vessel 112 may have a vessel length L,which may be a distance measured in the +/−X direction of the coordinateaxis of FIG. 7, and a vessel height H_(v), which may be a dimension ofthe distillation vessel 112 measured in the +/−Z direction of thecoordinate axis of FIG. 7. In some embodiments, the distillation vessel112 may be cylindrical in shape so that the vessel height H_(v) may be adiameter of the distillation vessel 112. The distillation vessel 112 mayhave an aspect ratio defined as the vessel length L divided by thevessel height H_(v). The distillation vessel 112 may have an aspectratio L/H_(v) of from 2 to 5, from 2 to 4.5, from 2 to 4, from 2 to 3.5,from 2.5 to 5, from 2.5 to 4.5, from 2.5 to 4, or even from 2.5 to 3.5.

As previously discussed, the distillation system 110 may include atleast one short-path distillation column 190 in fluid communication withthe vapor space 114 of the distillation vessel 112. The distillationsystem 110 may include a single short-path distillation column 190.Although schematically depicted in FIG. 7 as having a single short-pathdistillation column 190, the distillation system 110 may also include aplurality of short-path distillation columns 190 arranged in parallel,where each of the short-path distillation columns 190 may be in fluidcommunication with the vapor space 114 of the distillation vessel 112.For instance, the distillation system 110 may include 2, 3, 4, or morethan 4 short-path distillation columns 190 in fluid communication withthe distillation vessel 112.

Each of the short-path distillation columns 190 may have a number oftheoretical stages of from 1 to 5, such as from 1 to 4, from 1 to 3,from 2 to 5, from 2 to 4, from 2 to 3, from 3 to 5, or from 3 to 4.Short-path distillation may be utilized to distill thermally unstablecompounds at increased temperature and reduced pressure or to purifyvery small amounts of chemicals. Short-path distillation may becharacterized by a reduced distance that the distillate must travelbefore condensing at the condenser 130 compared to conventionaldistillation. In other words, the short-path distillation column 190 mayhave a reduced distance between ebullition of the hetero-azeotropemixture 122 and the condensation of the vapor phase at the condenser 130compared to conventional distillation processes. Reducing the distancebetween ebullition of the liquid and condensation of thehetero-azeotrope vapor phase may reduce the energy load associated withtransferring the hetero-azeotrope vapor phase from the distillationvessel 112 to the condenser 130.

Assuming the condenser 130 is positioned at the top 192 of the shortpath distillation column 190, the distance that the distillate travelsbefore condensing can be described in terms of a short-path ratio(H_(L):H_(T)), which can be defined as a ratio of a height (H_(L)) of avapor-liquid interface 118 from the bottom 113 of the distillationvessel 112 to a total height (H_(T)) of the short-path distillationcolumn 190, which is measured between the bottom 113 of the distillationvessel 112 and the top 192 of the distillation column 190. Theshort-path distillation column 190 may have a short-path ratiosufficient to reduce the energy associated with transferring the vaporphase to the condenser 130 and into the condensate receiver 140 (FIG.1). In some embodiments, the short-path distillation column 190 may havea short-path ratio (H_(L)/H_(T)) of from 0.2 to 0.5, from 0.2 to 0.45,from 0.2 to 0.4, from 0.25 to 0.5, from 0.25 to 0.45, from 0.25 to 0.4,from 0.3 to 0.5, from 0.3 to 0.45, or from 0.3 to 0.4.

As previously discussed, the distillation vessel 112 of the distillationsystem 110 may be in thermal communication with a heat source 116 (FIG.1). The heat source 116 may include waste heat from petroleum drilling,production, or refining operations. In petroleum drilling, production,and refining operations, waste heat may be readily available and mayprovide a reduced-cost source of energy for heating the hetero-azeotropemixture 122 in the distillation system 110. Additionally oralternatively, the heat source 116 may include a heat pump to furtherraise the temperature of the heat source 116 to a temperature sufficientto heat the hetero-azeotrope mixture 122 to the hetero-azeotrope boilingtemperature. The heat source 116 may also include heat from otherreduced cost heat sources, such as solar or geothermal heat. Forexample, in some embodiments, the method for desalinating an aqueousstream of the present disclosure may be used to desalinate seawater at alocation distant from any petroleum drilling, production, or refiningfacilities. In these embodiments, solar or geothermal heat sources maybe utilized to provide heat to the distillation system 110.

As shown in FIG. 7, the condenser 130 may be in fluid communication withthe short-path distillation column 190. The condenser 130 may be cooledto reduce the temperature of the hetero-azeotrope vapor, which may causethe hetero-azeotrope vapor to condense. The condenser 130 may be inthermal communication with a condenser heat exchanger 134, which may beoperable to provide a cooling fluid 136 to the condenser 130. Thecondenser heat exchanger 134 may be configured to recover heat from thecooling fluid returned from the condenser 130. The condenser 130 may becooled by passing cooling water, such as municipal water, well water,seawater, the incoming aqueous composition 102, or other process waterthrough the condenser 130. In the condenser 130, the hetero-azeotropevapor may be cooled to condense the hetero-azeotrope vapor to producethe multi-phase condensate 132. The condenser 130 may cool thehetero-azeotrope vapor to a temperature that is less than or equal tothe hetero-azeotrope boiling temperature of the hetero-azeotrope mixture122.

Although not shown in FIG. 7, the condensate receiver 140 (FIG. 1) maybe in fluid communication with the condenser 130 and may be configuredto receive the multi-phase condensate 132 from the condenser 130.Referring to FIGS. 8A-8D, many configurations or arrangements may beavailable for positioning the condenser 130 and condensate receiver 140relative to the short-path distillation column 190. Referring to FIG.8A, the condenser 130 may be disposed inside of an uppermost portion 194of the short-path distillation column 190, which may be the end of theshort-path distillation column 190 proximate the top 192. In theseconfigurations, the condensate receiver 140 may be positioned within theshort-path distillation column 190 and directly below the condenser 130.In operation, hetero-azeotrope vapor may be condensed by the condenser130 and the multi-phase condensate 132 may flow downward (in the −Zdirection of the coordinate axis of FIG. 8A) to the condensate receiver140. The aqueous phase 142 of the multi-phase condensate 132 may collectin the bottom of the condensate receiver 140, and at least a portion ofthe aqueous phase 142, which includes the desalinated water, may beremoved from the condensate receiver 140 through desalinated waterstream 146. In FIG. 8A, the condensate receiver 140 may be open-toppedor may have one or more weirs so that the entrainer-rich phase 144 ontop of the aqueous phase 142 can overflow the condensate receiver 140 tobe refluxed back to the short-path distillation column 190.

Referring now to FIG. 8B, the condenser 130 may extend upward at anangle from the uppermost portion 194 of the short-path distillationcolumn 190. In these arrangements, the condensate receiver 140 may bepositioned outside of the short-path distillation column 190 and influid communication with a lowermost end 138 of the condenser 130 sothat the multi-phase condensate 132 flows downward along the walls ofthe condenser 130 and collects in the condensate receiver 140. Thelowermost end 138 of the condenser 130 may be proximate the short-pathdistillation column 190. As shown in FIG. 8B, at portion of the aqueousphase 142 may be removed from the condensate receiver 140 in thedesalinated water stream 146. At least a portion of the entrainer-richphase 144 may be refluxed back to the short-path distillation column 190through the entrainer recycle stream 148. In some instances, all of theentrainer-rich phase 144 may be refluxed back to the short-pathdistillation column 190.

Referring to FIG. 8C, the condenser 130 may extend downward at an anglefrom the uppermost portion 194 of the short-path distillation column190. In these configurations, the lowermost end 138 of the condenser 130may be positioned away from the short-path distillation column 190. Thecondensate receiver 140 may be positioned outside of the short-pathdistillation column 190 and in fluid communication with a lowermost end138 of the condenser 130 so that the multi-phase condensate 132 flowsdownward along the walls of the condenser 130 and collects in thecondensate receiver 140. As shown in FIG. 8C, the aqueous phase 142 maybe removed from the condensate receiver 140 in the desalinated waterstream 146. At least a portion of the entrainer-rich phase 144 may berefluxed back to the short-path distillation column 190 through theentrainer recycle stream 148.

Referring now to FIG. 8D, the condenser 130 and condensate receiver 140may be integrated into a single condenser vessel 198 fluidly coupled tothe uppermost portion 194 of the short-path distillation column 190 by achannel 199. The condenser 130 may be disposed within the condenservessel 198 and positioned above (in the +Z direction of the coordinateaxis of FIG. 8D) the channel 199, and the condensate receiver 140 may bepositioned below the channel 199 (in the −Z direction of the coordinateaxis of FIG. 8D). The channel 199 may extend directly from theshort-path distillation column 190 to the condenser vessel 198 and mayhave a length of less than 1 meter (m), such as less than 0.5 m, lessthan 0.4 m, less than 0.3 m, less than 0.2 m, less than 0.1 m, or evenless than 0.05 m. As shown in FIG. 8D, the aqueous phase 142 may beremoved from the condensate receiver 140 in the desalinated water stream146. At least a portion of the entrainer-rich phase 144 may be refluxedback to the short-path distillation column 190 by overflowing from thecondensate receiver 140 into the channel 199, flowing through thechannel 199, and passing back into the short-path distillation column190. Other configurations and arrangements of the condenser 130 andcondensate receiver 140 are contemplated by this disclosure.

Referring again to FIG. 1, the condenser 130 may condense thehetero-azeotrope vapor into a multi-phase condensate 132. Themulti-phase condensate 132 may be collected in the condensate receiver140, in which the multi-phase condensate 132 may separate into at leasttwo distinct phases, which at least includes the aqueous phase 142 andthe entrainer-rich phase 144. The aqueous phase 142 may includedesalinated water. The desalinated water in the aqueous phase 142 mayhave a salinity of less than 1 g/L based on the total volume of theaqueous phase 142, such as less than 0.5 g/L, less than 0.1 g/L, lessthan 0.01 g/L, or even less than 0.001 g/L based on the total volume ofthe aqueous phase 142. In some embodiments, the desalinated water in theaqueous phase 142 may be free of salts. The aqueous phase 142 mayinclude some organic compounds, such as small quantities (less than 5wt. %) of the entrainers or other organic compounds from the aqueouscomposition 102 that are condensed in the condenser 130 and may be atleast partially soluble in the aqueous phase 142. For instance, theaqueous phase 142 may have less than 20 wt. %, less than 10 wt. %, oreven less than 1 wt. % organic compounds based on the total weight ofthe aqueous phase 142.

The entrainer-rich phase 144 may include the entrainer 120 condensed inthe condenser 130. The entrainer-rich phase 144 may also include smallconcentrations of other organic compounds from the aqueous composition102 that condense in the condenser 130. The aqueous phase 142 and theentrainer-rich phase 144 may be immiscible so that they separate into atleast two distinct liquid phases in the condensate receiver 140. In someembodiments, the aqueous phase 142 may have a greater density than theentrainer-rich phase 144, which may cause the aqueous phase 142 to sinkto the bottom of the condensate receiver 140 and the entrainer-richphase 144 to float on top of the aqueous phase 142. Although FIG. 1shows the aqueous phase 142 as having a greater density than theentrainer-rich phase 144, in some embodiments, the entrainer-rich phase144 may have a greater density than the aqueous phase 142 and may settleto the bottom of the condensate receiver 140 with the aqueous phase 142floating on top of the entrainer-rich phase 144. The density of theentrainer-rich phase 144 relative to the aqueous phase 142 may depend onthe density of the entrainer 120 introduced to form the hetero-azeotropemixture 122.

Referring again to FIG. 1, as previously discussed, the condensatereceiver 140 may include a separation system to separate the aqueousphase 142 and the entrainer-rich phase 144 from the multi-phasecondensate 132. The aqueous phase 142, the entrainer-rich phase 144, orboth may be separated from the multi-phase condensate 132. For example,the aqueous phase 142 may be separated from the multi-phase condensate132 by withdrawing at least a portion of the aqueous phase 142 out ofthe condensate receiver 140 as desalinated water stream 146. Theentrainer-rich phase 144 may be separated from the multi-phasecondensate 132 by withdrawing at least a portion of the entrainer-richphase 144 from the condensate receiver as the entrainer recycle stream148. In some embodiments, the aqueous phase 142, the entrainer-richphase 144, or both may be separated from the multi-phase condensate 132by decantation. Other separation processes may also be utilized toseparate the aqueous phase 142 or entrainer-rich phase 144 from themulti-phase condensate 132.

The separation system may include a level control system 152 operable tocontrol the level of the aqueous phase 142, the entrainer-rich phase144, or both in the condensate receiver 140. The level control system152 may include a level sensor (not shown) and one or more controlvalves (not shown) to control the flowrates of the desalinated waterstream 146, the entrainer recycle stream 148, or both to maintain thelevels of liquid phases within the condensate receiver 140. The levelcontrol system 152 may be operable to control the level of the aqueousphase 142 in the condensate receiver 140 in order to maintain a thinlayer of the entrainer-rich phase 144 on top of the aqueous phase 142.Alternatively or additionally, the level control system 152 may beoperable to control a withdrawal rate of the aqueous phase 142 from themulti-phase condensate 132 in the condensate receiver 140. Thecondensate receiver 140 may also include a vent or vapor outlet forventing desorbed gases 150 from the condensate receiver 140.

Referring still to FIG. 1, the aqueous phase 142 may be withdrawn fromthe condensate receiver 140 through desalinated water stream 146. Thedesalinated water of the desalinated water stream 146 may be directed toother processes without any further treatment or purification. Forinstance, the desalinated water of the desalinated water stream 146 maybe used as wash water for desalting crude oil without any furthertreatment.

The desalinated water stream 146 may be subjected to a further watertreatment process downstream of the condensate receiver 140 to removeorganic materials and other contaminants from the desalinated waterstream 146. As shown in FIG. 1, the desalinated water stream 146 may bepassed to a water treatment process 180, which may be operable to removeone or more than one contaminants from the desalinated water stream 146to produce purified desalinated water 182. The water treatment process180 may include, but is not limited to, reverse osmosis, adsorption onactivated carbon or other adsorbent, chemical treatment,nano-filtration, other water treatment process, or combinations of thesetreatment processes. In some embodiments, the method for desalinating anaqueous composition may include contacting the desalinated water stream146 with activated carbon. The water treatment process 180 may removeorganic compounds from the desalinated water stream 146 to purify andpolish the desalinated water stream 146 to produce the purifieddesalinated water 182. The purified desalinated water 182 from the watertreatment process 180 may be suitable for anthropological oragricultural use, such as by meeting water purity standards foranthropological or agricultural use.

As previously discussed, the entrainer-rich phase 144 may be recycledback to the distillation system 110 to provide at least a portion of theentrainer of the hetero-azeotrope mixture 122. The entrainer-rich phase144 may be recycled back to the distillation system 110 throughentrainer recycle stream 148. The entrainer-rich phase 144 may bewithdrawn from the condensate receiver 140 as the entrainer recyclestream 148. The entrainer recycle stream 148 may be refluxed back to theshort-path distillation column 190 of the distillation system 110, asshown in FIGS. 8A-8D. Alternatively or additionally, all or a portion ofthe entrainer recycle stream 148 may be passed back to the distillationvessel 112 of the distillation system 110 or to a pre-mix tank (notshown) upstream of the distillation vessel 112 to be combined with theaqueous composition 102 to form the hetero-azeotrope mixture 122, asshown in FIG. 1.

Some of the entrainer from the multi-phase condensate 132 may be lostfrom the system 100 through the desalinated water stream 146 or from thevent for removing desorbed gases 150 or other organic compounds having aboiling temperature less than the hetero-azeotrope boiling temperatureof the hetero-azeotrope mixture 122. Although the entrainer may beconsidered immiscible with water, the entrainer may have very lowsolubility in water, which may result in small amounts (less than 20g/100 g water, less than 10 g/100 g water, or even less than 1 g/100 gwater) of the entrainer being present in the aqueous phase 142. As aresult, these small amounts of entrainer 120 may be lost from the system100 through the desalinated water stream 146, which is passed out of thesystem 100. Small amounts of entrainer 120 may also be passed out of thesystem 100 through the distillation bottoms liquid 124, which will bedescribed subsequently in this disclosure. To compensate, thedistillation system 110 may include a make-up entrainer stream 121,which may be operable to introduce the entrainer 120 to the distillationvessel 112 to make up for the entrainer lost through the desalinatedwater stream 146 or distillation bottoms liquid 124.

Referring again to FIG. 1, the distillation system 110 may also producea distillation bottom liquid 124, which may include a mixture of waterand salts and may have salinity greater than the salinity of the aqueouscomposition 102. The distillation bottoms liquid 124 may also includeorganic compounds, such as a small portion of the entrainer 120 thatdissolves in the 102 in the distillation vessel 112, oil droplets,organic contaminants from the aqueous composition 102, other organiccompounds, or combinations of these. The distillation bottoms liquid 124may also include suspended solids, such as sand or rust particles, andthe inorganic contaminants from the aqueous composition 102, which havebeen described previously in this disclosure. The distillation bottomsliquid 124 may have a salinity of greater than or equal to 30 g/L, suchas greater than or equal to 50 g/L, greater than or equal to 100 g/L,greater than or equal to 150 g/L, or even greater than or equal to 200g/L. In some embodiments, the distillation bottoms liquid 124 may havesalinity of from 30 g/L to 500 g/L, from 50 g/L to 500 g/L, from 50 g/Lto 400 g/L, from 50 g/L to 300 g/L, from 100 g/L to 500 g/L, from 100g/L to 400 g/L, from 100 g/L to 300 g/L, from 150 g/L to 500 g/L, from150 g/L to 400 g/L, from 200 g/L to 500 g/L, from 200 g/L to 400 g/L, orfrom 200 g/L to 300 g/L.

Referring again to FIG. 1, the distillation bottoms liquid 124 may bewithdrawn from the distillation vessel 112 of the distillation system110. The distillation bottoms liquid 124 may be further processeddownstream of the distillation system 110. The distillation bottomsliquid 124 may be passed to a crystallization process 160, which may beoperable to separate at least a portion of the salt from thedistillation bottoms liquid 124 to produce a salt product 170 and abrine composition 172 having salinity less than the distillation bottomsliquid 124. For example, when the salinity of the distillation bottomsliquid 124 is greater than 150 g/L or even greater than or equal to 200g/L, the distillation bottoms liquid 124 may be passed to thecrystallization process 160 for separating salt from the distillationbottoms liquid 124 to reduce the salinity of the distillation bottomsliquid 124. When the distillation bottoms liquid 124 has a lessersalinity, such as a salinity less than 200 g/L or less than 150 g/L, thedistillation bottoms liquid 124 may be passed out of the system 100without being treated in the crystallization process 160. In someembodiments, the distillation bottoms liquid 124 may be passed through aheat exchanger or heat pump to remove heat from the distillation bottomsliquid 124 prior to passing the distillation bottoms liquid 124 to thecrystallization process 160.

The crystallization process 160 may be a cooling effect crystallizationprocess in which crystallization of the salts in the distillationbottoms liquid 124 is accomplished by reducing the temperature of thedistillation bottoms liquid 124 to reduce the solubility of the salts inthe distillation bottoms liquid 124. The crystallization process 160 mayinclude a crystallizer 161 that may include a cooling jacket 162 orother system from removing heat from the distillation bottoms liquid 124to reduce the temperature of the distillation bottoms liquid 124, Thecooling jacket 162 may be fluidly coupled to a crystallizer heatexchanger 164 which may be operable to remove heat from the coolingfluid returned from the cooling jacket 162. The crystallizer heatexchanger 164 may include a heat pump for removing heat from the coolingfluid. Alternatively or additionally, the crystallizer heat exchanger164 may include a heat exchanger in which a cooling fluid returned fromthe cooling jacket 162 is brought into thermal communication with a coldsource, such as a secondary cooling fluid having a lesser temperaturecompared to the primary cooling fluid, to reduce the temperature of thecooling fluid. In some embodiments, the crystallizer 161 may be adouble-walled crystallizer and the crystallization process 160 may becooled using a direct cold source, such as a heat exchanger operatingwith a cooling fluid in a double-walled crystallizer 161. Thecrystallization process 160 may separate the distillation bottoms liquid124 into the salt product 170 and the brine composition 172. The brinecomposition 172 may be passed out of the system 100. The brinecomposition 172 may be combined with one or more aqueous streams to formthe aqueous composition 102 or at least a portion of the aqueouscomposition 102 introduced to the system 100.

Referring now to FIG. 9, the system 100 may include various heatmanagement systems for heat balancing the system 100 to improve theenergy efficiency of the system. For example, the condenser 130 mayinclude the condenser heat exchanger 134, which may be operable to cooland condense the hetero-azeotrope vapors from the distillation vessel112 using the aqueous composition 102 introduced to the system 100. Inoperation, the condenser heat exchanger 134 may pass the aqueouscomposition 102, which is at a temperature less than thehetero-azeotrope boiling temperature, in countercurrent flow relative tothe hetero-azeotrope vapors, which are initially at a greatertemperature than the hetero-azeotrope boiling temperature. In thecondenser heat exchanger 134, heat may be transferred from thehetero-azeotrope vapors to the aqueous composition 102, which increasesthe temperature of the aqueous composition 102 to produce a first heatedaqueous stream. The heat removal from the hetero-azeotrope vapors mayreduce the temperature of the hetero-azeotrope vapors, which may causethe vapors to condense to produce the multi-phase condensate 132.Transferring heat to the aqueous composition 102 may recover heat fromthe distillation system 110, which may be passed back to thedistillation system 110 through the first heated aqueous stream 202.

Additional heat from the distillation system 110 may be furtherrecovered from the distillation bottoms liquid 124 by passing thedistillation bottoms liquid 124 through heat exchanger 204 incountercurrent flow relative to the first heated aqueous stream 202. Inheat exchanger 204, heat may be transferred from the distillationbottoms liquid 124 to the first heated aqueous stream 202 to produce asecond heated aqueous stream 206 having a temperature greater than atemperature of the first heated aqueous stream 202. Heat removal fromthe distillation bottoms liquid 124 may cool the distillation bottomsliquid 124 to a temperature suitable for further processing or disposalof the distillation bottoms liquid 124. The second heated aqueous stream206 may be passed to the distillation vessel 112. Recovery of heat fromthe hetero-azeotrope vapors, the distillation bottoms liquid 124, orboth may decrease the energy consumption of the distillation system 110,which may increase increasing the overall energy efficiency of thesystem 100.

As previously discussed, waste heat from petroleum drilling, production,or refining operations may be used to provide a cheap source of energyfor operating the distillation system 110. Additionally, as shown inFIG. 9, a heat pump 210 may also be incorporated into the system 100 torecover heat for the distillation system 110 and pass the heat back tothe distillation vessel 112. In FIG. 9, the heat pump 210 may operate toremove heat from a cooling fluid passed through the cooling jacket 162of the crystallizer 161 and transfer the heat to a heating fluid whichis passed to the distillation vessel 112 for heating thehetero-azeotrope mixture 122 to the hetero-azeotrope boilingtemperature. Supplemental energy 220 may be input to the heat pump 210to meet the energy demand and account for thermal losses in the system100. The supplemental energy 220 may include electricity, which may bereadily available in most petroleum drilling, production, and refiningoperations, or other sources of energy, such as solar, wind, geothermal,hydroelectric, or combinations of these. In some embodiments, thesupplemental energy 220 may include co-energy sharing between twofacilities or with neighboring industries.

When the salinity of the aqueous composition 102 is greater than 200g/L, the greater concentration of salts of the aqueous composition 102may disturb or prevent the formation of the hetero-azeotrope and disruptthe hetero-azeotropic distillation carried out in the distillationsystem 110. Therefore, method of desalinating the aqueous composition102 may include reducing the salinity of the aqueous composition 102 orthe hetero-azeotrope mixture 122 to produce a reduced-salinityhetero-azeotrope mixture and a feedstream salt product. After reducingthe salinity of the hetero-azeotrope mixture 122 to produce thereduced-salinity hetero-azeotrope mixture, the method may furtherinclude subjecting the reduced-salinity hetero-azeotrope mixture todistillation in the distillation system 110 to produce the desalinatedwater.

Referring now to FIG. 10, a system 300 for desalinating the aqueouscomposition 102 that has high salinity greater than 200 g/L, may includedistillation feedstream crystallization process 310 for removing saltfrom and reducing the salinity of the hetero-azeotrope mixture 122. Thedistillation feedstream crystallization process 310 may include afeedstream crystallizer 312 configured to receive the aqueouscomposition 102 or the first heated aqueous stream 202. The feedstreamcrystallizer 312 may be configured to receive the entrainer recyclestream 148 from the condensate receiver 140 and to receive the make-upentrainer stream 121. The feedstream crystallizer 312 may be operable toform the hetero-azeotrope mixture 122 by combining the aqueouscomposition 102 (or first heated aqueous stream 202) and the entrainer,which may be passed to the feedstream crystallizer 312 in the entrainerrecycle stream 148, the make-up entrainer stream 121, or both. Thefeedstream crystallizer 312 may include an agitator 314, which mayfacilitate combination of the entrainer and the aqueous composition 102(or first heated aqueous stream 202) to produce the hetero-azeotropemixture 122.

The distillation feedstream crystallization process 310 may be operableto reduce a salinity of the hetero-azeotrope mixture 122 bycrystallizing at least a portion of the salts in the hetero-azeotropemixture 122 and separating the crystallized salts from thehetero-azeotrope mixture 122 to produce a feedstream salt product 318and a reduced-salinity hetero-azeotrope mixture 320. In someembodiments, the distillation feedstream crystallization process 310 maybe configured to crystallize salts from the hetero-azeotrope mixture 122through anti-solvent effect crystallization. Anti-solvent effectcrystallization refers to a process of precipitating salts from a brinesolution by introducing an organic solvent that reduces the solubilityof the salts in the brine solution. In the distillation feedstreamcrystallization process 310, the addition of the entrainer (e.g.,entrainer recycle stream 148, the make-up entrainer stream 121, or both)to the aqueous composition 102 (or first heated aqueous stream 202) mayreduce the solubility of salts in the aqueous composition 102 or firstheated aqueous stream 202, which may cause the salts to precipitate inthe feedstream crystallizer 312 due to the anti-solvent effect.Alternatively or additionally, the distillation feedstreamcrystallization process 310 may be operable to reduce the salinity ofthe hetero-azeotrope mixture 122 through cooling effect crystallization.As previously discussed, cooling effect crystallization relies onreducing the solubility of the salts in the hetero-azeotrope mixture 122by reducing the temperature of the hetero-azeotrope mixture 122. Whencooling effect crystallization is employed, the feedstream crystallizer312 may include a cooling jacket fluidly coupled to a cooling source forcooling the feedstream crystallizer 312. The distillation feedstreamcrystallization process 310 may be configured to operate using acombination of anti-solvent effect crystallization and cooling effectcrystallization to reduce the salinity of the hetero-azeotrope mixture122. Other methods and processes may be used in place of or incombination with crystallization to reduce the salinity of thehetero-azeotrope mixture 122 prior to hetero-azeotropic distillation(upstream of the distillation system 110).

The feedstream salt product 318 may include one or a plurality of thesalts present in the aqueous composition 102 introduced to the system300. The feedstream salt product 318 may be further processed downstreamof the distillation feedstream crystallization process 310 to removecontaminants, such as organic compounds, residual water, heavy metalcontaminants, or other contaminants. The reduced salinityhetero-azeotrope mixture 320 may have a reduced salinity compared to theaqueous composition 102. The reduced salinity hetero-azeotrope mixture320 may have salinity that does not disrupt or prevent formation of thehetero-azeotrope during distillation in the distillation system 110. Forinstance, the reduced salinity hetero-azeotrope mixture 320 may havesalinity of less than 200 g/L, such as less than 175 g/L, or even lessthan 150 g/L.

Referring still to FIG. 10, in operation of system 300, the aqueouscomposition 102 may be passed through the condenser 130 to remove heatfrom the hetero-azeotrope vapors. Passing the aqueous composition 102through the condenser 130 may transfer heat into the aqueous composition102 to produce the first heated aqueous stream 202 having a temperaturegreater than the temperature of the aqueous composition 102. In someembodiments, the aqueous composition 102 may bypass the condenser 130and be passed directly to the feedstream crystallizer 312. The firstheated aqueous stream 202 may be passed to the feedstream crystallizer312 of the distillation feedstream crystallization process 310, wherethe first heated aqueous stream 202 may be combined with the entrainerfrom the entrainer recycle stream 148, the make-up entrainer stream 121,or both to form the hetero-azeotrope mixture 122. In the feedstreamcrystallizer 312, the hetero-azeotrope mixture 122 may be subjected tocrystallization to remove salt from the hetero-azeotrope mixture 122,thereby decreasing the salinity of the hetero-azeotrope mixture 122 toproduce the reduced salinity hetero-azeotrope mixture 320. Thecrystallized salt may be passed out of the feedstream crystallizer 312as the feedstream salt product 318. The reduced salinityhetero-azeotrope mixture 320 may be passed from the distillationfeedstream crystallization process 310 to the distillation system 110,where the reduced salinity hetero-azeotrope mixture 320 may be subjectedto hetero-azeotropic distillation in the distillation system 110 aspreviously described in relation to FIG. 1.

As shown in FIG. 10, the hetero-azeotrope vapor 131 from thehetero-azeotropic distillation may be passed from the distillationvessel 112 or short-path distillation column 190 to the condenser 130where the hetero-azeotrope vapor 131 is condensed to form themulti-phase condensate 132. The multi-phase condensate 132 may be passedto the condensate receiver 140, where the multi-phase condensate 132 maybe separated into the aqueous phase 142 and the entrainer-rich phase144. In system 300, at least a portion of the entrainer-rich phase 144may be passed back to the feedstream crystallizer 312 of thedistillation feedstream crystallization process 310 as the entrainerrecycle stream 148 to produce the hetero-azeotrope mixture 122. At leasta second portion of the entrainer-rich phase 144 may be refluxed back tothe distillation system 110. The distillation bottoms liquid 124 may bepassed to the crystallization process 160 as previously described inrelation to FIG. 1.

Referring to FIG. 11, the method may include reducing a salinity of theaqueous composition 102 prior to combining the aqueous composition 102with the entrainer 120 to form the hetero-azeotrope mixture 122. Theaqueous composition 102 may be passed initially to an aqueouscomposition crystallization process 410 in which the salinity of theaqueous composition 102 may be reduced by crystallizing salts from theaqueous composition 102 through cooling effect crystallization. Theaqueous composition crystallization process 410 may include an aqueouscomposition crystallizer 412 having an agitator 414 and a cooling jacket430. The cooling jacket 430 may be in operable communication with acooling source 432, such as a cooling fluid source, for passing acooling fluid through the cooling jacket 430. The cooling source 432 maybe a heat exchanger, heat pump, cooling fluid source, or combinations ofthese. Cooling fluid sources may include water sources, such asmunicipal water, well water, seawater, produced water, process watersources, or other sources of cooling water. In some embodiments, thecooling source 432 may be closed loop cooling circuit. The coolingsource 432 may include a heat pump 460 which may be operable to removeheat from a cooling fluid circulated through the cooling jacket 430. Insome embodiments, the aqueous composition crystallizer 412 may not be influid communication with a make-up entrainer stream. Instead, themake-up entrainer stream may be introduced to the distillation vessel112 downstream of the aqueous composition crystallization process 410.

The aqueous composition crystallization process 410 may be operable toremove salts from the aqueous composition 102 to produce an aqueouscomposition salt product 418 and a reduced-salinity aqueous composition440. The aqueous composition salt product 418 may include one or aplurality of the salts present in the aqueous composition 102 introducedto the system 400. The aqueous composition salt product 418 may befurther processed downstream of the aqueous composition crystallizationprocess 410 to remove contaminants, such as organic compounds, residualwater, heavy metal contaminants, or other contaminants. In someembodiments, the aqueous composition salt product 418 may be removed andrecovered from the system 400.

The reduced-salinity aqueous composition 440 may have a reduced salinitycompared to the aqueous composition 102. The reduced-salinity aqueouscomposition 440 may have salinity that does not disrupt or preventformation of the hetero-azeotrope during distillation in thedistillation system 110. The reduced-salinity aqueous composition 440may have salinity of less than 200 g/L, such as less than 175 g/L, oreven less than 150 g/L. The reduced-salinity aqueous composition 440 maybe passed out of the aqueous composition crystallization process 410 andmay be passed to the distillation system 110.

The reduced-salinity aqueous composition 440 may be passed through oneor more heat exchangers, such as the condenser 130, the heat exchanger450 coupled to heat pump 460, other heat exchanger, or combinations ofheat exchangers, to recover heat from the distillation system 110 andimprove the energy efficiency of the system 400. Passing thereduced-salinity aqueous composition 440 through the condenser 130, heatexchanger 450, other heat exchanger, or combinations of these mayincrease the temperature of the reduced-salinity aqueous composition 440to produce a heated reduced-salinity aqueous composition 442, which maythen be passed to the distillation system 110. The reduced-salinityaqueous composition 440 or the heated reduced-salinity aqueouscomposition 442 may be combined with the entrainer 120 in thedistillation vessel 112 to form the hetero-azeotrope mixture 122. Themake-up entrainer stream 121 may be fluidly coupled to the distillationvessel 112. The entrainer 120 may be supplied by the entrainer recyclestream 148 recycled from the condensate receiver 140 to the distillationvessel 112, from the make-up entrainer stream 121 introduced to thedistillation vessel 112, or both. In some embodiments, the make-upentrainer may be introduced to the aqueous composition crystallizer 412.In these embodiments, the amount of make-up entrainer added to theaqueous composition 102 in the aqueous composition crystallizer 412 maynot be sufficient by itself to effect anti-solvent crystallization ofthe aqueous composition 102.

Although the distillation system 110, crystallization process 160, andfeedstream crystallization processes (distillation feedstreamcrystallization process 310 and aqueous composition crystallizationprocess 410) are described in this disclosure in terms of single unitoperations, it is understood that any of these processes may includemultiple processes operated in parallel or in series to produce thedesalinated water. For example, in some embodiments the distillationsystem 110 may include a plurality of distillation vessels 112 and aplurality of short-path distillation columns 190. The plurality ofdistillation vessels 112 and short-path distillation columns 190 may beoperated in series or in parallel. Each of the crystallization processesdescribed in the present disclosure may also include multiplecrystallizers operated in series or in parallel. Additionally, in someembodiments, the distillation system 110 may include multipledistillation vessels 112 and multiple short-path distillation columns190 operated in parallel or in series and a single crystallizationprocess 160 capable of crystallizing the distillation bottoms liquid 124from one or all of the plurality of distillation vessels 112. Otherconfigurations, combinations, and arrangements of the unit operationsdescribed in the present disclosure for producing desalinated water froman aqueous composition 102 comprising a salt are contemplated. Thenumber of processes operated in parallel or in series may depend on theproduction rate of desalinated water.

The systems and methods described in the present disclosure may producedesalinated water for use as process water in petroleum drilling,production, or refining operations. For example, the desalinated waterproduced by the systems and methods of the present disclosure may beused for desalting crude oil. The desalinated water may be treated toremove the residual organic compounds to produce treated desalinatedwater that may be suitable for use in drilling operations, such as foruse in drilling fluids or injection fluids for example, or in firesuppression systems, stripping columns, or other refining uses. Withadditional treatments and purification, the treated desalinated watermay be suitable for various anthropologic or agricultural uses as well.

EXAMPLES

The following examples illustrate the separation of desalinated waterfrom an aqueous stream originating from a petroleum processing operationthrough hetero-azeotrope distillation and investigate the effects ofvarious parameters on the distillation temperature and separationefficiency of the hetero-azeotrope distillation process.

Experimental Apparatus

Referring to FIG. 12, an experimental hetero-azeotrope distillationsystem 500 for conducting the experiments in the following examples isschematically depicted. The experimental hetero-azeotrope distillationsystem 500 included a three-necked round-bottom flask 510 fitted with aDean-Stark apparatus 520 and a bulb condenser 540. The potentialuncondensed gases 542, such as desorbed gases or uncondensed entrainer,was collected at the top of the condenser 540 and directed to an exhaustsystem equipped with treatment systems to remove organics and othercontaminants. The flask 510 was configured to contain thehetero-azeotrope mixture 122 and the temperature of the hetero-azeotropemixture was measured using a K-type thermocouple 550 connected to anelectronic read-out 552. The temperature of the hetero-azeotrope vaporentering the Dean-Stark apparatus 520 was measured using a coloredalcohol thermometer 560 situated at the top of the Dean-Stark apparatus520. The Dean-Stark apparatus 520 included a column 522 extending fromthe flask 510 and a condensate receiver 524 fluidly coupled to thecolumn 522 and configured to collect the condensate from the bulbcondenser 540. The condensate included the aqueous phase 142(desalinated water) and, optionally, the entrainer-rich phase 144. TheDean-Stark apparatus 520 included a three-way tap 526, which could beswitched “Off” to collect the condensate including the aqueous phase 142(desalinated water) and, optionally, the entrainer-rich phase 144,“On-Out” to collect the aqueous phase 142 (desalinated water) from spout528, or “On-In” to steer the aqueous phase 142 (distilled water) and/orthe entrainer-rich phase 144 back into the flask 510. A cooling fluid544 was passed through the bulb condenser 540 to cool thehetero-azeotrope vapors to promote condensation. The experimentalhetero-azeotrope distillation system 500 included a heating device 570for heating the flask 510 and an external stirrer 580.

Example 1 Effects of the Volume Fraction of Aqueous Composition on theThermal Behavior and Distillation Rate of the Hetero-Azeotrope Mixture

In Example 1, the effects of variation in the volume fraction of theaqueous composition in a binary hetero-azeotropic mixture wereinvestigated. In Example 1, a fixed amount of 206 mL of toluene was usedas the entrainer. The aqueous composition of Example 1 was collectedfrom an oily, briny water stream produced by a Gas Oil Separation Plant(GOSP) for processing crude oil. The aqueous composition had a salinityof 107 g/L. The volume fractions of the aqueous composition in eachhetero-azeotrope mixture of Example 1 are provided in Table 2. Thetemperatures of the vapor phase, the temperature of the hetero-azeotropemixture 122 (bulk liquid), and the amount of water collected in theDean-Stark apparatus 520 were measured and plotted as functions of time(x-axis) in FIGS. 13, 14, 15, and 16.

Referring to FIG. 13, the temperature of the hetero-azeotrope mixture122 in the bulk liquid (y-axis) is graphically depicted as a function ofthe time (y-axis) in seconds. FIG. 13 shows the evolution of thetemperature of the hetero-azeotrope mixture with time to the boilingtemperature. Before the temperature stabilized at the boilingtemperature, the heating rate of the hetero-azeotrope mixture wasdetermined from the initial slope of the curves and was found to averageabout 0.11±0.01 degrees Celsius per second (° C./s). As shown by FIG.13, the volume fraction of the aqueous composition in the binaryhetero-azeotrope mixture had little or no effect on thetemperature-changing rate of the hetero-azeotrope mixture.

Once the temperature stabilized, desalinated water condensed by the bulbcondenser 540 was collected in the condensate receiver 524 of theDean-Stark apparatus 520. The volume of the desalinated water collectedwas recorded as a function of time. Referring to FIG. 14, the volume ofdesalinated water collected (y-axis) was plotted as a function of time(x-axis) starting at the time when the temperature reached the boilingtemperature (about 1000 seconds). The rate of distillation wasgraphically determined from FIG. 14 for each of the hetero-azeotropemixtures of Example 1. The rates of distillation in units of millilitersper hour (mL/hr) for each hetero-azeotrope mixture in Example 1 areprovided in Table 2.

TABLE 2 Volume Percent of Aqueous Composition and Rate of Distillationfor the Water/Toluene Hetero-Azeotrope Mixtures of Example 1 VolumeReference Percent of Rate of Mixture Number in Aqueous Distillation IDFIGS. 13-16 Composition (%) (mL/hr) 1A 1202 9.6 39.96 1B 1204 13.8 52.201C 1206 17.6 67.68 1D 1208 21.1 59.76 1E 1210 24.3 61.20 1F 1212 27.251.12

The rate of distillation was greatest when the water/toluenehetero-azeotrope mixture had a volume percent of the aqueous compositionof 17.6 vol. %. This is illustrated graphically in FIG. 14 by thegreater slope of data series 1206, which corresponds to the volumepercent of the aqueous composition of 17.6 vol. %, relative to the otherdata sets. The volume percent of aqueous composition of 17.6 vol. % canbe considered the hetero-azeotrope volume percent of the aqueouscomposition. As shown in Table 2, decreasing the volume percent of theaqueous composition in the mixture below the hetero-azeotrope volumepercent of the aqueous composition in the mixture caused the rate ofdistillation to significantly decrease. For example, when the volumefraction of the aqueous composition was reduced by half from 17.6 vol. %to 9.6 vol. %, the distillation rate decreased by 41%. The rate ofdistillation also decreases when the volume percent of the aqueouscomposition is greater than the hetero-azeotrope volume percent of water(17.6% vol.), but the decrease in the rate of distillation is lesscompared to the decrease in rate of distillation for volume percentagesof the aqueous composition below the hetero-azeotrope volume percent.For example, when the volume percent of the aqueous composition isincreased from 17.6 vol. % to 24.3 vol. %, the rate of distillation onlydecreased by 9%.

FIG. 15 graphically depicts the temperature of the vapor phase (y-axis)for each hetero-azeotrope mixture of Example 1 as a function of time(x-axis). The hetero-azeotrope boiling point temperature of aToluene/Water hetero-azeotrope is known to be in the range of 83° C. to85° C. and is indicated in FIG. 15 by the rectangle 1220. Regardless ofthe composition, the vapor phase temperatures for the hetero-azeotropemixtures of Example 1 all stabilized in the range of thehetero-azeotrope boiling temperature of a Toluene/Waterhetero-azeotrope, which indicates that the vapor composition is at thehetero-azeotropic composition (approximately 20% weight in water). Inother words, the amount of the aqueous composition in thehetero-azeotrope mixture 122 has very little or no effect on thetemperature and composition of the vapor phase after stabilization.

For Sample 1A in which the volume percent of the aqueous composition was9.6 vol. %, the vapor phase temperature began to increase after 2100seconds. At this point in time, the volume percent of the aqueouscomposition remaining in the flask 510 for Sample 1A was only 3.7 vol. %(about 8 mL). The mass concentration of salts in the aqueous compositionin the hetero-azeotrope mixture increased from 107 g/L of dissolved saltin Sample 1A at time equal to zero (9.6 vol. % aqueous composition) to296 g/L of dissolved salt in the 8 mL of the aqueous compositionremaining at time equal to 2100 seconds. Although some precipitatedsalts were observed in the flask during the experiment starting at timeequal to about 1600 seconds, the precipitation of salt was moresignificant after cooling the remaining water-depleted bulk liquid toroom temperature.

Referring now to FIG. 16, the temperature of the hetero-azeotropemixture 122 (bulk liquid) (y-axis) is graphically depicted as a functionof time (x-axis) for time greater than 1000 seconds, which illustratesthe temperature behavior of the hetero-azeotrope mixture (bulk liquid)after ebullition began. For Sample 1A 1202 (9.6 vol. % aqueouscomposition), the hetero-azeotrope mixture began to vaporize at atemperature of 96° C.±1° C. However, in Sample 1A, the excess toluene,which has a boiling temperature of 110° C., resulted in a steadyincrease in the temperature of the bulk liquid at a temperature-changingrate of 3.96×10⁻³ ±0.01×10⁻³° C./s, during ebullition of thehetero-azeotrope mixture. For Samples 1B (1204) and 1C (1206) (13.8 vol.% and 17.6 vol. % aqueous composition respectively), thehetero-azeotrope vaporized when the temperature of the hetero-azeotropemixture reached 94° C.±1° C. For samples 1B and 1C, the temperaturebehavior of the bulk liquid after time equal to 1000 seconds wascontrolled by ebullition of the hetero-azeotrope, which resulted intemperature-changing rates of 2.35×10⁻³±0.01×10⁻³° C./s for Sample 1Band 2.43×10⁻³±0.01×10⁻³° C./s for Sample 1C, respectively. Thesetemperature-changing rates for Samples 1B and 1C were less than thetemperature-changing rate for Sample 1A, which had an excess of toluene.This indicates that the temperature-changing of Samples 1B and 1C wascontrolled by ebullition of the hetero-azeotrope rather than beinggoverned by excess toluene or excess water.

Still referring to FIG. 16, for Samples 1D (1208) and 1E (1210) (21.1vol. % and 24.3 vol. % aqueous composition, respectively), the thermalbehavior of the hetero-azeotrope mixture (bulk liquid) was influenced bythe excess aqueous composition, which had a boiling temperature of 104°C. The hetero-azeotrope vaporized when the hetero-azeotrope mixtureapproached temperatures of 102° C.±1° C. for Sample 1D and 100° C.±1° C.for Sample 1E. The temperature of the hetero-azeotrope mixture began todecrease after about 800 seconds for Sample 1D and after around 1200seconds for Sample 1E. For Samples 1D and 1E, the temperature-changingrates are not constant with time because the variations in thecomposition of the hetero-azeotrope mixture with time are more complex.Not intending to be bound by any particular theory, it is believed thatdistillation of the hetero-azeotrope mixtures of Samples 1D and 1Ehaving concentrations of the aqueous composition of 21.1 vol. % and 24.3vol. %, respectively, changed the composition, and therefore thetemperature, of the liquid with time in the direction of a mixturehaving a composition closer to the hetero-azeotropic composition for atoluene/water heteroazeotrope.

For Sample 1F (1212) having 27.2 vol. % aqueous composition in thehetero-azeotrope mixture, the excess of aqueous composition in thehetero-azeotrope mixture resulted in the temperature of thehetero-azeotrope mixture remaining stable at 102° C.±1° C. in the systemduring the whole duration of the experiment. The hetero-azeotropevaporized when the bulk temperature approached 102° C.±1° C. No othersignificant changes were observed in this case.

Example 2 Effects of the Volume Fraction of Entrainer on the ThermalBehavior of the Hetero-Azeotrope Mixture

In Example 2, the effects of the volume fraction of the entrainer on thethermal behavior and distillation rate of the binary hetero-azeotropicmixture were investigated. In Example 2, a fixed amount of 44 mL of theoily, briny water stream from Example 1 having a salinity of 107 g/L wasused as the aqueous composition. Varying amounts of toluene were addedto the 44 mL of the aqueous composition to prepare the hetero-azeotropemixtures of Example 2. The volume fractions of the entrainer in eachhetero-azeotrope mixtures of Example 2 are provided in Table 3. Thetemperatures of the vapor phase, the temperature of the hetero-azeotropemixture 122 (bulk liquid), and the amount of water collected in theDean-Stark apparatus 520 were measured and plotted as functions of time(x-axis) in FIGS. 17, 18, 19, and 20.

FIG. 17 graphically depicts the evolution of the bulk temperature withtime to the boiling point temperature of the hetero-azeotrope mixture122. The temperature-changing rates of each of the hetero-azeotropemixtures, before stabilization of the temperature, were determined fromthe initial slope of the curves in FIG. 17. The average initialtemperature-changing rate was determined to be 0.17° C./s±0.09° C./sbefore stabilization of the temperature. It was found that the volumepercent of the entrainer had very little or no effect on thetemperature-changing rate of the hetero-azeotrope mixtures beforeebullition.

Once the temperature stabilized, desalinated water condensed by the bulbcondenser 540 was collected in the condensate receiver 524 of theDean-Stark apparatus 520. The volume of the desalinated water collectedwas recorded as a function of time. Referring to FIG. 18, the volume ofdesalinated water collected (y-axis) was plotted as a function of time(x-axis) starting at the time when the temperature reached the boilingtemperature (about 1000 seconds). The rate of distillation wasgraphically determined from FIG. 18 for each of the hetero-azeotropemixtures of Example 2. The rates of distillation in units of millilitersper hour (mL/hr) for each hetero-azeotrope mixture in Example 2 areprovided in Table 3.

TABLE 3 Volume Percent of Entrainer and Rate of Distillation for theWater/Toluene Hetero-Azeotrope Mixtures of Example 2 Reference VolumeRate of Mixture Number in Percent of Distillation ID FIGS. 17-20Entrainer (%) (mL/hr) 2A 1302 90.0 39.96 2B 1304 86.2 52.20 2C 1306 82.467.67 2D 1308 77.3 59.76 2E 1310 70.1 55.44 2F 1312 53.7 51.12

Although the compositions of Samples 2A-2F of Example 2 are differentthan the compositions of Example 1, the trend in the rate ofdistillation is similar to trend observed in Example 1. For thehetero-azeotrope mixtures of Example 2, the rate of distillation wasgreatest at the hetero-azeotropic composition of the binarytoluene/water mixture, which was observed for Sample 2C having 82.4 vol.% toluene entrainer. Increasing the volume percent of toluene, as inSamples 2A and 2B resulted in significant decreases in the rate ofdistillation. For example, increasing volume percent of toluene israised from 82.4 vol. % to 90.0 vol. % decreased the distillation rateby 41%. Although the rate of distillation also decreased when the volumefraction of toluene was decreased to less than the hetero-azeotropicvolume fraction of toluene (less than 82.4 vol. %) as in Samples 2D to2F, the decrease in the rate of distillation was not as significantcompared to increasing the volume percent of toluene to greater than thehetero-azeotropic composition. For example, decreasing the volumefraction of toluene from 82.4 vol. % to 70.1 vol. % (Sample 2E) resultedin a decrease in the rate of distillation of only 18%.

FIG. 19 graphically depicts the temperature of the vapor phase (y-axis)for each hetero-azeotrope mixture of Example 2 as a function of time(x-axis). The hetero-azeotrope boiling point temperature of atoluene/water hetero-azeotrope is known to be in the range of 83° C. to85° C. and is indicated in FIG. 19 by the rectangle 1320. Regardless ofthe composition, the vapor phase temperatures for the hetero-azeotropemixtures of Example 2 all stabilized in the range of thehetero-azeotrope boiling temperature of a Toluene/Waterhetero-azeotrope, which indicates that the vapor composition is at thehetero-azeotropic composition (approximately 20% by weight water). Inother words, the amount of toluene entrainer in the hetero-azeotropemixture 122 has very little or no effect on the temperature andcomposition of the vapor phase after stabilization.

In Example 2 in which the volume percent of toluene was changed, noprecipitation of salts in the hetero-azeotrope mixtures was observed. InExample 2, the mass concentration of dissolved salts in thehetero-azeotrope mixtures reached a maximum of 197 g/L, which is lessthan the solubility limit of the salts in water, which may be about 350g/L at 25° C.

Referring now to FIG. 20, the temperatures of the hetero-azeotropemixtures 122 (bulk liquid) (y-axis) of Example 2 are graphicallydepicted as functions of time (x-axis) for time greater than 1000seconds, which illustrates the temperature behavior of thehetero-azeotrope mixtures (bulk liquid) of Example 2 after ebullitionbegan. For Sample 2F having 53.7 vol. % of toluene entrainer in thehetero-azeotrope mixture, the hetero-azeotrope mixture vaporized as soonas the bulk temperature reached 102° C.±1° C. Following the start ofebullition, the excess water, which had a boiling temperature of 104°C., influenced the thermal behavior of the hetero-azeotrope mixture. Thedecrease in the temperature of the hetero-azeotrope mixture of Sample 2Foccurred after approximately 1200 seconds. For Sample 2F, thetemperature of the hetero-azeotrope mixture does not vary linearly withtime. Not intending to be bound by any particular theory, it is believedthat distillation of the hetero-azeotrope mixture of Sample 2F having53.7 vol. % toluene changed the composition, and therefore thetemperature, of the liquid with time in the direction of a mixturehaving a composition closer to the hetero-azeotropic composition for atoluene/water hetero-azeotrope.

Referring to FIG. 20, for Sample 2A having 90.0 vol. % tolueneentrainer, the hetero-azeotrope vaporized as soon as the bulktemperature of the hetero-azeotrope mixture reached 96° C.±1° C.Following the start of ebullition, the excess of toluene, which has aboiling point temperature of 110° C., governed the thermal behaviorresulting in an increase in the bulk temperature of the hetero-azeotropemixture. The temperature-changing rate for the hetero-azeotrope mixtureof Sample 2A was determined to be 3.96×10⁻³° C./s±0.01×10 ⁻³° C./s,during the ebullition of the hetero-azeotrope.

Referring still to FIG. 20, for Samples 2B through 2E, which representthe range of from 70.1 vol. % to 86.2 vol. % toluene in thehetero-azeotrope mixture, each of the hetero-azeotrope mixtures began tovaporize when the bulk temperature of the hetero-azeotrope mixturereached 95° C.±1° C. In this range of toluene volume percent, ebullitionof the hetero-azeotrope controlled the thermal behavior of thehetero-azeotrope mixture. The temperature-changing rates for Samples 2B,2C, 2D, and 2E were determined to be 2.43×10⁻³° C./s±0.01×10⁻³° C./s(2B), 2.35×10⁻³° C./s±0.01×10⁻³° C./s (2C), 1.37×10⁻³° C./s±0.01×10⁻³°C./s(2D), and 1.48×10⁻³° C./s±0.01×10⁻³° C./s (2E).

As a summary of Examples 1 and 2, the vapor temperatures for thehetero-azeotrope mixtures of Examples 1 and 2 comprising toluene and theaqueous composition having a salinity of 107 g/L were all in the rangeof from 83° C. to 85° C., which is in the vicinity of the knownhetero-azeotrope boiling temperature of 84° C. for the toluene/waterhetero-azeotrope. Thus, the amount of the aqueous composition and theamount of entrainer do not affect the formation of the hetero-azeotrope.However, the relative amounts of the aqueous composition and theentrainer can affect the bulk temperature of the hetero-azeotropemixture and the energy consumption of the distillation process. Theminimum bulk temperature of the hetero-azeotrope mixture was observedwhen the relative amount of the aqueous composition and the entrainer(toluene) was at, or close to, the hetero-azeotropic composition (44 mLof aqueous composition and 206 mL of toluene, which corresponds to 17.6vol. % aqueous composition and 82.4 vol. % toluene). It was also foundthat this optimal minimum bulk temperature of the hetero-azeotropemixture was stable with a small deviation in the quantity of water, from−25% vol to 0% vol, and a large variation in the amount of toluene, from−50% vol to +33% vol. The effect of the volume of water on the bulktemperature required for the distillation of the hetero-azeotrope wasfound to be stronger than the effect of the volume of entrainer(toluene).

Example 3 Effect of Salinity of the Aqueous Composition on the ThermalBehavior and Distillation Rate of the Hetero-Azeotrope Mixture

In Example 3, the effects of salinity of the aqueous composition on thethermal behavior and distillation rate of the hetero azeotrope mixturewere investigated. Distillation was performed on a hetero-azeotropemixtures having a fixed ratio of the aqueous compositions to the tolueneentrainer. The aqueous compositions used in Example 3 included distilledwater (Sample 3A) and 3 different produced water samples collected fromthree different petroleum production operations and having threedifferent salinities (Samples 3B, 3C, and 3D). The average salinity foreach of the aqueous compositions of Example 3 is provided in Table 4.The amount of water collected in the Dean-Stark apparatus 520, thetemperatures of the vapor phase, and the temperature of thehetero-azeotrope mixture 122 (bulk liquid) were measured and plotted asfunctions of time (x-axis) in FIGS. 21, 23, and 24.

Once the temperature stabilized, desalinated water condensed by the bulbcondenser 540 was collected in the condensate receiver 524 of theDean-Stark apparatus 520. The volume of the desalinated water collectedwas recorded as a function of time. Referring to FIG. 21, the volume ofdesalinated water collected (y-axis) was plotted as a function of time(x-axis) starting at the time when the temperature reached the boilingtemperature (at time just greater than about 800 seconds). Before thetemperature stabilized, the temperature-changing rate for thehetero-azeotrope mixtures of Example 3 were determined to be 0.12°C./s±0.01° C./s.

FIG. 21 graphically depicts the amount of water collected (y-axis) as afunction of time (d-axis). The rate of distillation was graphicallydetermined from FIG. 21 for each of the hetero-azeotrope mixtures ofExample 3. The rates of distillation in units of milliliters per hour(mL/hr) for each hetero-azeotrope mixture in Example 3 are provided inTable 4.

TABLE 4 Salinity and Rate of Distillation for the Hetero-AzeotropeMixtures of Example 3 Reference Salinity Average Rate of Sample Numberin Range Salinity Distillation ID FIGS. 21, 23, 24 (g/L) (g/L) (mL/hr)3A 1402 0 0 68.40 3B 1404  92-123 107 67.68 3C 1406 169-216 192 63.36 3D1408 274-336 305 62.28

Referring to FIG. 22, the distillation rate (y-axis) as a function ofsalinity (x-axis) from the data in Table 4 is graphically depicted. InFIG. 22, a curve 1420 was fitted to the experimental data. The bestcurve fitting for these data points was a standard 4-parameter logisticequation expressed by the following Equation 1 (EQU. 1):

$\begin{matrix}{y = {d + \frac{\left( {a - d} \right)}{\left( {1 + \left( \frac{x}{c} \right)^{b}} \right)}}} & {{EQU}.\mspace{14mu} 1}\end{matrix}$

In EQU. 1, y is the rate of distillation, x is the average salinity, anda, b, c, d are the curve fitting parameters. The fitting target is thelowest sum of squared absolute error (Err.). The curve fitting resultedin the values for a, b, c, and d in Table 5.

TABLE 5 Curve Fitting Parameters for Distillation Rate Curve of Example3 Shown in FIG. 22 Parameter Value a 68.40 b 5.97 c 150.34 d 62.19 Err.5.05 × 10⁻²⁹

As shown in FIG. 22, the salinity of the aqueous composition affects therate of distillation. As the salinity of the aqueous compositionincreases from 0 g/L to above 300 g/L, the rate of distillationdecreases by about 9%. Two characteristic points of curve weregraphically determined by locating the intersections of three tangentiallines. First tangential line 1422 was drawn tangent to curve 1420 at thestart of curve 1420 at Sample 3A 1402, for which the salinity is 0 g/L.The second tangential line 1424 was drawn tangent to curve 1420 at theinflection point 1410 of the curve 1420. The third tangential line 1426was drawn tangent to curve 1420 at the end point of the curverepresented by Sample 3D 1408 (average salinity of 305 g/L). The firstintersection 1430 provides an estimation of a starting point of thedeceleration of the distillation rate, which may occur at a salinity ofthe aqueous phase of about 98 g/L. The second intersection 1432estimates an ending point of the decrease in distillation rate, whichmay occur at a salinity of the aqueous phase of about 202 g/L, leadingto a stabilization of the distillation rate.

These same transition points are observed in the evolution of the vaportemperature for each of the hetero-azeotrope mixtures of Example 3. FIG.23 graphically depicts the temperature of the vapor phase (y-axis) foreach hetero-azeotrope mixture of Example 3 as a function of time(x-axis) starting at time greater than about 800 seconds. Thehetero-azeotrope boiling point temperature of a toluene/waterhetero-azeotrope is known to be in the range of 83° C. to 85° C. and isindicated in FIG. 23 by the rectangle 1220. For Sample 3A (1402,salinity of 0 g/L) and Sample 3B (1404, average salinity of 107 g/L),the temperature of the vapor phase was maintained within the range of83° C. to 85° C., which indicated that the toluene/waterhetero-azeotrope was the product being distilled.

For Sample 3C (1406), the temperature of the vapor phase started out inthe range of 83° C. to 85° C., which indicates that the initialdistillation involved distillation of the toluene/waterhetero-azeotrope. At around 1100 seconds, salts precipitation wasobserved when the concentration of salts in the hetero-azeotrope mixtureof Sample 3C reached 206 g/L. After approximately 1400 seconds, thevapor temperature increased and the concentration of salts in theaqueous composition reached 235 g/L. This observation suggested that thevapor composition is going away from the vapor composition of thetoluene/water hetero-azeotrope when the salt concentration reaches about235 g/L.

Still referring to FIG. 23, for Sample 3D (1408, salinity of 305 g/L),the vapor temperature continuously increased throughout thedistillation. This result demonstrates that the greater salinity ofSample 3D, which was in excess of 235 g/L, disrupted the formation ofthe hetero-azeotrope and no hetero-azeotrope was formed during theexperiment. At around 1100 seconds, salts precipitation was observedwhen the salt concentration of the solution reached 353 g/L.

Referring now to FIG. 24, the temperatures of the hetero-azeotropemixtures 122 (bulk liquid) (y-axis) of Example 3 are graphicallydepicted as functions of time (x-axis) for time greater than 1000seconds. FIG. 24 graphically demonstrates that the stabilizedtemperature of the hetero-azeotrope mixture increases with increasingsalinity of the aqueous composition.

In summary, from Example 3, it was discovered that the salinity of theaqueous composition has a significant effect on the distillation of thehetero-azeotrope mixture. The vapor temperature does not stabilize nearthe boiling point temperature of the hetero-azeotrope, such as at atemperature of about 84° C. for a toluene/water azeotrope, when theaqueous composition has salinity equal to or greater than 202 g/L.Example 3 demonstrates that salinity of the aqueous composition ofgreater than about 202 g/L interferes with formation of thehetero-azeotrope resulting in failure to form the hetero-azeotrope.

Example 4 Ternary Hetero-Azeotrope

In Example 4, the performance of a ternary hetero-azeotrope on thehetero-azeotrope distillation process compared to a binaryhetero-azeotrope was evaluated. For Example 4, the ternaryhetero-azeotrope mixtures of Example 4 included the aqueous compositiondescribed in Example 1 (salinity equal to 107 g/L) and toluene andn-pentane as the entrainers. The total volume of each of the ternaryhetero-azeotrope mixtures of Example 4 was 250 mL and three differentvolumetric fractions of the aqueous composition, toluene, and n-pentanewere evaluated. These specific compositions for Example 4 were chosenbased on the ternary hetero-azeotrope phase equilibrium diagram of FIG.29, which is at ambient pressure (about 101.3 kPa). The compositions ofExample 4 are provided in Table 6. In particular, the compositions forExample 4 were selected to be compositions along the line 1530 in FIG.29, which are within the azeotrope envelope between the pentane/waterand the toluene/water hetero-azeotropes. The amount of water collectedin the Dean-Stark apparatus 520, the temperatures of the vapor phase,and the temperature of the hetero-azeotrope mixture 122 (bulk liquid)were measured and plotted as functions of time (x-axis) in FIGS. 25, 26,27, and 28.

TABLE 6 Volume Percent of Entrainers and Rate of Distillation for theWater/Toluene/N-Pentane Ternary Hetero- Azeotrope Mixtures of Example 4Ref. Aqueous Rate of Sample No. In Composition Toluene N-pentaneDistillation ID FIGS. 25-28 (vol. %) (vol. %) (vol. %) (mL/hr) 4A 1502100.0 0.0 0.0 — 4B 1504 60.0 22.0 18.0 13.03 4C 1506 32.0 37.6 30.4 7.094D 1508 9.6 49.8 40.4 5.40

FIG. 25 graphically depicts the evolution of the bulk temperature of theternary heteroazeotrope mixtures of Example 4 (y-axis) with time(x-axis) to the boiling point temperature for each of the ternaryhetero-azeotrope mixtures. The temperature-changing rates of each of theternary hetero-azeotrope mixtures, before stabilization of thetemperature, were determined from the initial slope of the curves inFIG. 25. The average initial temperature-changing rate was determined tobe 0.06° C./s±0.01° C./s before stabilization of the temperature. It wasfound that the composition of the ternary mixture had very little or noeffect on the temperature-changing rate of the hetero-azeotrope mixturesbefore stabilization of the temperature.

Referring now to FIG. 26, the temperatures of the ternaryhetero-azeotrope mixtures (bulk liquid) (y-axis) are graphicallydepicted as functions of time (x-axis) for time greater than 1000seconds (region A in FIG. 25), which illustrates the temperaturebehavior of the ternary hetero-azeotrope mixtures (bulk liquid) ofExample 4 after reaching the initial boiling point temperature. Sample4A designated by reference number 1502 in FIG. 26 represents the thermalbehavior of the aqueous composition by itself with no entrainers.

For Sample 4B (1504) having 60 vol % aqueous composition, the ternaryhetero-azeotrope mixture was observed to start vaporizing when thetemperature reached 104° C.±1° C. As shown in FIG. 26, the temperatureof the bulk liquid of the ternary hetero-azeotrope of Sample 4B wasconstant throughout the experiment. It is believed that this constantboiling temperature for the ternary hetero-azeotrope mixture of Sample4B was the result of the excess amount of aqueous composition remainingin the flask 510. For Sample 4C (1506), which included 37.6 vol. %aqueous composition, the ternary hetero-azeotrope mixture startedvaporizing at around 80° C.±1° C. At around 1900 seconds, thetemperature rapidly increased by about 10° C. It is believed that thisincrease in temperature of the ternary hetero-azeotrope mixture ofSample 4C may be due to shifting of the composition of the feed mixturecaused by flooding of the condensate receiver 524 of the Dean-Starkapparatus 520 during the experiment. When the condensate is collected inthe condensate receiver 524, water started to move towards the bottom ofthe condensate receiver 524 while the lighter toluene and pentaneaccumulated in the upper section of the condensate receiver 524. Thus,when the condensate receiver floods, only the toluene/pentane mixture isrecycled back to the ternary hetero-azeotrope mixture in the flask 510.Once flooding of the condensate receiver 524 commenced, the temperatureof the ternary hetero-azeotrope mixture in the flask 510 continued toincrease with time at a temperature-changing rate of1.77×10⁻³±0.01×10⁻³° C./s. For Sample 4D (1508) having 9.6 vol % aqueouscomposition, the ternary hetero-azeotropic mixture began to vaporize ataround 60° C.±1° C. The temperature continued to increase which isbelieved to be the result of the excess amount of the homogenous mixtureof toluene and pentane left in the flask 510. The temperature-changingrate for Sample 4D was estimated to be 1.8×10⁻³±0.01×10⁻³° C./s duringthe ebullition of the ternary hetero-azeotrope mixture.

Once the temperature stabilized, condensed desalinated water wascollected in the condensate receiver 524 and the volume recorded as afunction of time. Referring to FIG. 27, the volume of desalinated watercollected (y-axis) was plotted as a function of time (x-axis). The rateof distillation was graphically determined from FIG. 27 for each of theternary hetero-azeotrope mixtures of Example 4 and the results of thedistillation rate for each ternary hetero-azeotrope mixture in Example 4is listed in Table 6, which was previously provided in this disclosure.The distillation for Sample 4A having 100 vol. % aqueous composition wasnot determined. As shown by the different slopes for the differentternary hetero-azeotrope mixtures shown in FIG. 27, it is noted that thedistillation rate increases with increasing volume percent of theaqueous composition.

The maximum distillation rate was found to be 13.03 mL/hr correspondingto Sample 4B, which had a ternary hetero-azeotrope mixture compositionof 60.0 vol. % aqueous composition, 22.0 vol. % toluene, and 18.0 vol. %n-pentane. When the volumetric fractions of toluene and pentane weremore than doubled in Sample 4D, the resulting distillation rate was lessthan half of the maximum distillation rate for Sample 4B. Referring toSample 4C, the distillation rate also decreased when the volumetricfractions of toluene and pentane were increased to 37.6 vol. % and 30.4vol. %, respectively. Thus, the distillation rate can be increased forthe ternary hetero-azeotrope by decreasing the volume proportion of theentrainers.

Referring to FIG. 28, the temperature of the vapor phase (y-axis) as afunction of time (x-axis) is graphically depicted. As shown in FIG. 28,the temperature of the vapor phase remained generally constant, whichindicated that the vapor phase is at a hetero-azeotropic composition.The temperatures of the vapor phase were within the range of temperaturebetween the hetero-azeotrope boiling temperature for pentane/waterbinary hetero-azeotrope (34.09° C.) and the hetero-azeotrope boilingtemperature of the toluene/water binary hetero-azeotropes (84.03° C.).The temperature of the vapor phase at the maximum distillation rate wasabout 55° C. It may be noted from FIG. 28 that the temperature of thevapor phase for Sample 4C having 32.0 vol. % aqueous composition beganto decrease at around 2,600 seconds. As previously discussed, it isbelieved that this may have resulted from changes in the ternaryheteroazeotrope mixture composition caused by flooding of the condensatereceiver 524. After 3,000 seconds, the temperature of the vapor phasefor Sample 4C began to increase slightly and stabilized at theazeotropic temperature of 55° C. For Sample 4D having 9.6 vol. % aqueouscomposition, the temperature of the vapor phase began to increase moredramatically after about 5200 seconds. It is believed that this increasein the temperature of the vapor phase may also be the result of changingcomposition of the ternary hetero-azeotropic mixture. It can be notedfrom FIG. 28 that Sample 4D with 9.6 vol. % aqueous composition was notazeotropic and composition shifted away from the azeotropic compositionas the amount of water decreased in the flask 510.

In a first aspect of the present disclosure, a method for desalinatingan aqueous composition includes forming a hetero-azeotrope mixture bycombining at least a portion of the aqueous composition with at leastone entrainer, the at least a portion of the aqueous compositioncomprising at least one salt. The method further includes subjecting thehetero-azeotrope mixture to distillation at a distillation temperatureof less than a boiling temperature of the aqueous composition at anoperating distillation pressure, which results in separation of thehetero-azeotrope mixture into a distillation bottoms liquid and amulti-phase condensate. The method further includes recovering themulti-phase condensate, the multi-phase condensate comprising anentrainer-rich phase and an aqueous phase, the aqueous phase comprisingdesalinated water; and removing at least a portion of the aqueous phasefrom the multi-phase condensate to recover the desalinated water.

A second aspect of the present disclosure may include the first aspect,in which the aqueous composition is briny water having a salinity offrom 3 grams per liter (g/L) to 300 g/L.

A third aspect of the present disclosure may include the second aspect,in which the briny water comprises at least one of seawater, saltywastewater, produced water from hydrocarbon drilling, production orrefining operations, or combinations of these.

A fourth aspect of the present disclosure may include any of the firstthrough third aspects, further comprising separating at least a portionof the entrainer-rich phase from the multi-phase condensate and passingthe at least a portion of the entrainer-rich phase back to thehetero-azeotrope mixture.

A fifth aspect of the present disclosure may include any of the firstthrough fourth aspects, in which the hetero-azeotrope mixture comprisesfrom 20 volume percent (vol. %) to 95 vol. % aqueous composition basedon a total volume of the hetero-azeotrope mixture.

A sixth aspect of the present disclosure may include any of the firstthrough fifth aspects, in which the hetero-azeotrope mixture has ahetero-azeotrope boiling temperature of less than 100° C. at theoperating distillation pressure.

A seventh aspect of the present disclosure may include any of the firstthrough sixth aspects, in which the at least one entrainer is chemicallystable and does not react with water, at least one salt, or organiccompounds in the aqueous composition.

An eighth aspect of the present disclosure may include any of the firstthrough seventh aspects, in which the at least one entrainer has asolubility in water of less than 20 grams per 100 grams of water at 25°C. and atmospheric pressure.

A ninth aspect of the present disclosure may include any of the firstthrough eighth aspects, in which the entrainer comprises one or morethan one of an alkane, an alkene, an aromatic, an ester, an alcohol, athiol, a disulfide, a sulfide, an ether, a ketone, a nitro group, orcombinations of these.

A tenth aspect of the present disclosure may include any of the firstthrough ninth aspects, in which the entrainer is selected from2-methyl-1,3-butadiene; pentane; 2-methyl-2-butene;methylenecyclobutane; carbon disulfide; 1-hexene; ethyl formate;4-methyl-2-pentene; 3-methyl-3-buten-1-ol; hexane; isopropyl ether;cis-1-butenyl ethyl ether; 1-butenyl methyl ether; benzene; cyclohexane;ethyl acetate; cyclohexene; methyl propanoate; propyl formate; isopropylacetate; ethylbutyl ether; isopropylacetate; butyl ethyl ether;1-heptene; 2,5-dimethylfuran; 2,2,4-trimethylpentane; heptane; isobutylformate; methylisopropenyl ketone; diisobutylene; propyl acetate;3-pentanone; allyl acetate; nitroethane; 2,6-dimethyl-4-heptanol;toluene; 1,2-propanediol diacetate; butyl isopropenyl ether;2-methyl-2-butanol; methylisobutyl ketone; isobutyl acetate;2-methylpropyl acetate; cyclopropyl methyl ketone; propyl propanoate;octane; isobutyl alcohol; 2-pentanol, or combinations of theseentrainers.

An eleventh aspect of the present disclosure may include any of thefirst through tenth aspects, in which the at least one entrainer doesnot include halogen-containing compounds, amines, nitriles, acetals,vinyl ethers, or aldehydes.

A twelfth aspect of the present disclosure may include any of the firstthrough eleventh aspects, where forming the hetero-azeotrope mixturecomprises combining the aqueous composition with a plurality ofentrainers.

A thirteenth aspect of the present disclosure may include any of thefirst through twelfth aspects, in which the distillation comprises shortpath distillation in which a short path ratio (H_(L)/H_(T)) of from 0.2to 0.5, in which the short path ratio is defined as a height (HL) of avapor-liquid interface from a bottom of a distillation vessel to a totalheight (HT), which includes a distance from the bottom of thedistillation vessel to a top of a short path distillation column coupledto the distillation vessel.

A fourteenth aspect of the present disclosure may include any of thefirst through thirteenth aspects, in which subjecting thehetero-azeotrope mixture to distillation is conducted in a distillationvessel having an aspect ratio (L/H_(v)) of from 2 to 5, in which theaspect ratio of the distillation vessel is defined as a length (L) ofthe distillation vessel divided by a height (H_(v)) of the distillationvessel.

A fifteenth aspect of the present disclosure may include any of thefirst through fourteenth aspects, in which the aqueous composition hassalinity greater than 200 grams per liter (g/L) and the method furthercomprises reducing the salinity of the hetero-azeotrope mixture toproduce a reduced salinity hetero-azeotrope mixture and a feedstreamsalt product, and subjecting the reduced salinity hetero-azeotropemixture to the distillation to produce the multi-phase condensate.

A sixteenth aspect of the present disclosure may include any of thefirst through fifteenth aspects, further comprising subjecting the atleast a portion of the aqueous phase to a water treatment process toremove contaminants from the at least a portion of the aqueous phase toproduce a purified desalinated water.

A seventeenth aspect of the present disclosure may include any of thefirst through sixteenth aspects further comprising subjecting at least aportion of the distillation bottoms liquid to crystallization whichresults in separation of the distillation bottoms liquid into a saltproduct and a brine composition.

In an eighteenth aspect, a system for desalinating an aqueouscomposition includes a distillation system comprising a distillationvessel in thermal communication with a heat source and a condenser influid communication with the distillation vessel. The system furtherincludes a condensate receiver in fluid communication with the condenserand operable to receive a multi-phase condensate comprising at least anaqueous phase and an entrainer-rich phase from the distillation system.The condensate receiver may include a separation system operable toseparate at least a portion of an aqueous phase from the condensate. Thesystem further comprises a crystallizer in fluid communication with thedistillation vessel, the crystallizer operable to receive a bottomsliquid from the distillation vessel and separate at least a portion of asalt in the bottoms liquid to produce a salt product and a brinecomposition.

A nineteenth aspect of the present disclosure may include the eighteenthaspect, in which the distillation vessel comprises an aqueouscomposition inlet and an entrainer inlet and the distillation vessel isoperable to combine the aqueous composition and an entrainer to producea hetero-azeotrope mixture.

A twentieth aspect of the present disclosure may include the eighteenthor nineteenth aspects, in which the distillation system furthercomprises a short-path distillation column in fluid communication withthe distillation vessel and disposed between the distillation vessel andthe condenser.

A twenty-first aspect of the present disclosure may include any of theeighteenth through twentieth aspects, further comprising a feedstreamcrystallizer disposed upstream of the distillation vessel and in fluidcommunication with the distillation vessel, the feedstream crystallizeroperable to combine the aqueous composition and an entrainer to producea hetero-azeotrope mixture and to remove at least a portion of a saltfrom the hetero-azeotrope mixture to produce a feedstream salt productand a reduced-salinity hetero-azeotrope mixture.

A twenty-second aspect of the present disclosure may include any of theeighteenth through twenty-first aspects, in which the condensatereceiver comprises a level control system operable to control awithdrawal rate of at least a portion of an aqueous phase from themulti-phase condensate in the condensate receiver.

It should now be understood that various aspects of the systems andmethods for desalinating aqueous stream having one or more salts thatinclude hetero-azeotropic distillation are described and such aspectsmay be utilized in conjunction with various other aspects.

Throughout this disclosure ranges are provided for various processingparameters and operating conditions for the systems and methods ofdesalinating aqueous streams and compositions of various streams andmixtures. It will be appreciated that when one or more explicit rangesare provided the individual values and the sub-ranges formed within therange are also intended to be provided as providing an explicit listingof all possible combinations is prohibitive. For example, a providedrange of 1-10 also includes the individual values, such as 1, 2, 3, 4.2,and 6.8, as well as all the ranges which may be formed within theprovided bounds, such as 1-8, 2-4, 6-9, and 1.3-5.6.

It should be apparent to those skilled in the art that variousmodifications and variations can be made to the described embodimentswithout departing from the spirit and scope of the claimed subjectmatter. Thus, it is intended that the specification cover themodifications and variations of the various described embodimentsprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method for desalinating an aqueous composition,the method comprising: forming a hetero-azeotrope mixture by combiningat least a portion of the aqueous composition with at least oneentrainer, the at least a portion of the aqueous composition comprisingat least one salt; subjecting the hetero-azeotrope mixture todistillation at a distillation temperature of less than a boilingtemperature of the aqueous composition at an operating distillationpressure, which results in separation of the hetero-azeotrope mixtureinto a distillation bottoms liquid and a multi-phase condensate;recovering the multi-phase condensate, the multi-phase condensatecomprising an entrainer-rich phase and an aqueous phase, the aqueousphase comprising desalinated water; and removing at least a portion ofthe aqueous phase from the multi-phase condensate to recover thedesalinated water.
 2. The method of claim 1, in which the aqueouscomposition is briny water having a salinity of from 3 grams per liter(g/L) to 300 g/L.
 3. The method of claim 2, in which the briny watercomprises at least one of seawater, salty wastewater, produced waterfrom hydrocarbon drilling, production or refining operations, orcombinations of these.
 4. The method of claim 1, further comprising:separating at least a portion of the entrainer-rich phase from themulti-phase condensate; and passing the at least a portion of theentrainer-rich phase back to the hetero-azeotrope mixture.
 5. The methodof claim 1, in which the hetero-azeotrope mixture comprises from 20volume percent (vol. %) to 95 vol. % aqueous composition based on atotal volume of the hetero-azeotrope mixture.
 6. The method of claim 1,in which the hetero-azeotrope mixture has a hetero-azeotrope boilingtemperature of less than 100° C. at the operating distillation pressure.7. The method of claim 1, in which the at least one entrainer ischemically stable and does not react with water, at least one salt, ororganic compounds in the aqueous composition.
 8. The method of claim 1,in which the at least one entrainer has a solubility in water of lessthan 20 grams per 100 grams of water at 25° C. and atmospheric pressure.9. The method of claim 1, in which the entrainer comprises one or morethan one of an alkane, an alkene, an aromatic, an ester, an alcohol, athiol, a disulfide, a sulfide, an ether, a ketone, a nitro group, orcombinations of these.
 10. The method of claim 1, in which the entraineris selected from 2-methyl-1,3-butadiene; pentane; 2-methyl-2-butene;methylenecyclobutane; carbon disulfide; 1-hexene; ethyl formate;4-methyl-2-pentene; 3-methyl-3-buten-1-ol; hexane; isopropyl ether;cis-1-butenyl ethyl ether; 1-butenyl methyl ether; benzene; cyclohexane;ethyl acetate; cyclohexene; methyl propanoate; propyl formate; isopropylacetate; ethylbutyl ether; isopropylacetate; butyl ethyl ether;1-heptene; 2,5-dimethylfuran; 2,2,4-trimethylpentane; heptane; isobutylformate; methylisopropenyl ketone; diisobutylene; propyl acetate;3-pentanone; allyl acetate; nitroethane; 2,6-dimethyl-4-heptanol;toluene; 1,2-propanediol diacetate; butyl isopropenyl ether;2-methyl-2-butanol; methylisobutyl ketone; isobutyl acetate;2-methylpropyl acetate; cyclopropyl methyl ketone; propyl propanoate;octane; isobutyl alcohol; 2-pentanol, or combinations of theseentrainers.
 11. The method of claim 1, where forming thehetero-azeotrope mixture comprises combining the aqueous compositionwith a plurality of entrainers.
 12. The method of claim 1, in which thedistillation comprises short path distillation in which a short pathratio (H_(L)/H_(T)) of from 0.2 to 0.5, in which the short path ratio isdefined as a height (H_(L)) of a vapor-liquid interface from a bottom ofa distillation vessel to a total height (H_(T)), which includes adistance from the bottom of the distillation vessel to a top of a shortpath distillation column coupled to the distillation vessel.
 13. Themethod of claim 1, in which subjecting the hetero-azeotrope mixture todistillation is conducted in a distillation vessel having an aspectratio (L/H_(v)) of from 2 to 5, in which the aspect ratio of thedistillation vessel is defined as a length (L) of the distillationvessel divided by a height (H_(v)) of the distillation vessel.
 14. Themethod of claim 1, further comprising subjecting at least a portion ofthe distillation bottoms liquid to crystallization which results inseparation of the distillation bottoms liquid into a salt product and abrine composition.
 15. The method of claim 1, in which the aqueouscomposition has salinity greater than 200 grams per liter (g/L) and themethod further comprises: reducing the salinity of the hetero-azeotropemixture to produce a reduced salinity hetero-azeotrope mixture and afeedstream salt product; and subjecting the reduced salinityhetero-azeotrope mixture to the distillation to produce the multi-phasecondensate.
 16. A system for desalinating an aqueous composition, thesystem comprising: a distillation system comprising a distillationvessel in thermal communication with a heat source and a condenser influid communication with the distillation vessel; a condensate receiverin fluid communication with the condenser and operable to receive amulti-phase condensate comprising at least an aqueous phase and anentrainer- rich phase from the distillation system, the condensatereceiver comprising a separation system operable to separate at least aportion of an aqueous phase from the condensate; and a crystallizer influid communication with the distillation vessel, the crystallizeroperable to receive a bottoms liquid from the distillation vessel andseparate at least a portion of a salt in the bottoms liquid to produce asalt product and a brine composition.
 17. The system of claim 16, inwhich the distillation vessel comprises an aqueous composition inlet andan entrainer inlet and the distillation vessel is operable to combinethe aqueous composition and an entrainer to produce a hetero-azeotropemixture.
 18. The system of claim 16, in which the distillation systemfurther comprises a short-path distillation column in fluidcommunication with the distillation vessel and disposed between thedistillation vessel and the condenser.
 19. The system of claim 16,further comprising a feedstream crystallizer disposed upstream of thedistillation vessel and in fluid communication with the distillationvessel, the feedstream crystallizer operable to combine the aqueouscomposition and an entrainer to produce a hetero-azeotrope mixture andto remove at least a portion of a salt from the hetero-azeotrope mixtureto produce a feedstream salt product and a reduced-salinityhetero-azeotrope mixture.
 20. The system of claim 16, in which thecondensate receiver comprises a level control system operable to controla withdrawal rate of at least a portion of an aqueous phase from themulti-phase condensate in the condensate receiver.